SEC Frequently Asked Questions

General Questions about Space Weather

1. What is space weather?
2. Where does the Sun's energy come from?
3. What is a solar flare?
4. What is a geomagnetic storm?
5. Does ALL solar activity impact Earth? Why or why not?
6. How far is the Sun from the Earth?
7. How do solar flares reach Earth?
8. How strong is solar wind (compared to wind on Earth)?
9. What are the different layers of the Sun and what are the layers of the Earth's atmosphere?
10. Can you compare space weather to weather on Earth?
11. Have scientists seen changes in the intensity of space weather?
12. What are sunspots and how do they relate to space weather?
13. What is the solar max and solar min?
14. What are the northern lights and are they related to space weather?
15. Why are some regions on the Sun more active than others?
16. How do you forecast space weather?
17. Why is forecasting space weather important?
18. When do the effects of space weather show up?
19. How long have scientists known about space weather?
20. What is the role of the Space Environment Center?
21. How do you monitor events on the sun?
22. What types of industries might be impacted by space weather and how?
23. Can solar storms hurt people?
24. Can the damage of solar storms be prevented?
25. Is space weather "all bad" or are there some positive impacts?
26. Where can I get more information?

Understanding Solar Phenomena

1. What satellites observe the sun that have data we can look?
2. Please explain flare classification.

Effects on Earth Systems

1. I'd like to know what impact mass coronal ejections and solar flares have on Earth's weather conditions.
2. Is there a relationship between solar events and earthquakes?
3. How bright is the aurora and how can I demonstrate it?

Effects on Satellite

1. How does the "South Atlantic Anomaly" affect satellites?

Effects on Power Systems

1. What caused the failure of the Canadian power plant in March 1989?
2. How could I demonstrate the effect of space weather on power systems?
3. How sensitive does a meter have to be to sense voltage in an induced current?

Effects on Animals

1. Is it true that migratory birds are affected by space weather?

NOAA Space Weather Scales

1. What is the difference between the number of events per cycle and the days per cycle.
2. How would one find out how many of each event have occurred in the current cycle?
3. At what point is a cycle considered ended and a new cycle has begun?
4. What are the effects on mid-latitude power systems from Geomagnetic Storms?
5. What are the units for flux levels in Solar Radiation Storms?
6. What type of particles are measured for Solar Radiation Storms?
7. Do the effects of Solar Radiation Storms differ based on latitude?
8. How are the three NOAA scales related?

ACE Real-Time Solar Wind

1. What is special about the ACE satellite
2. Did NOAA provide any funding for the ACE RTSW system?
3. Did NOAA provide any funding for the ACE RTSW ground system put together by SEC and how does the RTSW ground system work?
4. What control do we have over the ACE RTSW data and over the ground system?
5. Could they send ACE off after a comet or something like they did for ISEE-3?
6. What is the average delay time from the time the data leaves ACE until it is fully processed and into the operations center?
7. What kind of problems do we have in obtaining the goal of 96 % daily coverage with no gap larger than 15 minutes?

General Questions about Space Weather

Answered by the Students of 2nd Year Physics at Fairview High School with expert comments in italics.

1. What is space weather?

Space weather originates on the sun. Activity on the surface of the sun, such as solar flares, can cause high levels of radiation in space. This radiation can come as plasma (particles) or electromagnetic radiation (light).
2. Where does the Sun's energy come from?
The sun's energy comes from nuclear fusion in the sun's central core. Fusion is the collision of atoms at high temperature and speed causing them to become one atom and release energy. -student
3. What is a solar flare?
Though scientists are not sure of what causes solar flares, they do know that they are bursts of electromagnetic radiation. These bursts, which appear in an 11-year cycle, produce radio waves which penetrate the Earth's atmosphere, often disrupting radio transmissions on Earth. -student

We think the energy for a solar flare comes from the magnetic energy associated with strong fields on the Sun.- JK

4. What is a geomagnetic storm?
A geomagnetic storm occurs when unusually strong surges of solar wind (charged particles from the sun) hit the Earth. This effect causes variations in the magnetic field which surrounds the Earth. -student
5. Does ALL solar activity impact Earth? Why or why not?
Not all solar activity affects the Earth because the Earth's magnetic field repels most of the solar wind. Occasionally solar flares, prominences, and coronal holes (holes in the sun's atmosphere) send high levels of electromagnetic radiation toward the Earth in the form of X-rays. -student

Some activity, like mass ejections, are directional. Earth may not be in the path of a particular ejection so all activity does not affect Earth. -JK

6. How far is the Sun from the Earth?
The sun varies in its distance from Earth. On average it is 149,000,000,000 meters from the Earth, or 92,600,000 miles. -student
7. How do solar flares reach Earth?
A solar flare happens when a large amount of plasma from the sun's surface is ejected outwards. When the plasma returns to the suns surface, it collides with denser material found in the chromosphere. This collision releases large amounts of energy in the form of x-rays and other wavelengths which travel toward the earth at the speed of light. Sometimes the plasma does not return to the sun, but instead travels towards the planet where it is deflected by the planets' magnetic fields. -student

Big ejections from the Sun can be 1-10 billion tonnes, moving at 400-1000 km/sec (approximately 1-2 million mph) and take more than a day to pass Earth, after the sudden onset (often a leading-edge shock wave)

8. How strong is solar wind (compared to wind on Earth)?
Unlike wind on Earth, solar wind is composed of highly charged particles ejected from the sun. Although the solar wind can be used to move spacecraft with "solar sails," the two different types of wind are very different. The solar wind is deflected by the earth's magnetic field, but it changes that field, compressing it on the sun-ward side and extending it away from the sun. -student

Solar sails are still a theoretical concept--there aren't any in use today. They would sail not on the solar wind but on the photon (light) pressure from the sun.

9. What are the different layers of the Sun and what are the layers of the Earth's atmosphere?
The innermost layer of the Sun is called the Core. Nuclear fusion, which creates the light the Sun emits, occurs within the Core, which has a temperature of 27 million degrees F (15 million C).

The second layer out is the radiative layer. This layer is like an insulator, and helps maintain the temperature of the core.

The third layer is the convective layer. The energy of the sun is carried further out from the core by convection in the layer.

The next layer is the photosphere, which is the part of the sun that we see with our eyes. Sunspots appear in the photosphere.

The fifth layer is the chromosphere which is darker than the photosphere and can only be seen during an eclipse. The chromosphere is where solar flares can best be seen.

The next layer is the corona which is comprised of two layers. The inner corona is a halo which extends millions of miles away from the sun. The corona is much hotter than the photosphere and produces x-rays. The outer corona extends to the earth and far beyond it. -student

10. Can you compare space weather to weather on Earth?
To a certain extent, space weather and earth weather are similar. For example, solar wind is much like wind on earth, except that it involves the movement of matter instead of air masses. Earth weather occurs and is contained in the earth's atmosphere. Space weather occurs in the sun's atmosphere, but may affect Earth's atmosphere. -student
11. Have scientists seen changes in the intensity of space weather?
Yes; sunspots, for example, change in intensity over an 11 year cycle. When solar flares occur, space weather activity increases dramatically. -student

At present, we are in the increasing phase of Cycle 23, which began in October 1996 and is expected to peak sometime during the year 2000. SEC scientists have noted a steady increase in the number of sunspot groups and solar flares, as well as other space weather occurrences like solar proton events and a rising 10.7 cm solar radio flux. We've had about a dozen episodes of intense space weather so far this cycle and we expect to see many more as Cycle 23 continues.-NC

12. What are sunspots and how do they relate to space weather?
Sunspots are not well understood, but scientist have some idea of what they are. Strong magnetic/electromagnetic activity is associated with sun spots. They are the coldest part of the sun, and usually develop in pairs. Sunspot activity is in an 11 year cycle. Currently, we are coming out of a low activity point, and more sunspots are beginning to appear. -student

The magnetic field in sunspots stores energy that is released in solar flares. As a result, flares usually occur in a cycle that mimics the eleven-year sunspot cycle. Other forms of space weather such as geomagnetic storms and proton radiation showers follow a similar cycle. Sunspots usually occur in groups-usually as simple pairs-but at times in complicated arrangements with many spots and complex shapes. These unusual regions most often produce solar flares. Space weather forecasters use the complexity and shapes of sunspots to make flare forecasts-the more complex the groups of spots, the more likely a flare will occur. -GH

13. What is the solar max and solar min?
Solar min and max refer to the eleven years sunspot cycle. Every eleven years there are noticeable spots on the surface of the sun. The spots decline to a minimum and then rise to a maximum on this eleven-year cycle. -student

At solar minimum, the sun may go many days with no spots visible. At maximum, there may be several hundred spots on any day.-GH

14. What are the northern lights and are they related to space weather?
The northern lights, also called the aurora borealis, is electromagnetic radiation caused by electrons colliding with molecules in the ionosphere. This spectrum of electromagnetic radiation ranges from infrared to ultraviolet. The visible spectrum is dominated by white and green light produced by excited oxygen molecules and pink light emitted from nitrogen. -student

When the sun is active, it often produces mass ejections that interact with Earth's magnetic field. Electric currents begin to flow in the upper atmosphere, and these currents produce the aurora borealis, which occurs almost simultaneously around both the north and south poles.-GH

15. Why are some regions on the Sun more active than others?
The sun goes through variations in climate much like the Earth does: cooler and hotter, denser and lighter regions interact together like ocean current. Remember that the sun is made of gases and has very strong magnetic tendencies. These tendencies react on the sun's surface like volcanoes and earthquakes here on earth, shifting matter and heat around in different places. -student

Because the sun is made up of gases and because it rotates once every approximately 27 days around its north-south axis, the regions around the equator tend to rotate faster than the areas near the poles. This differential rotation drives the mass motions described above.-GH

16. How do you forecast space weather?
Certain features on the sun, such as sun spots, are good indications of solar weather. By comparing the current sun spot patterns to those seen in the past, we can partially predict space weather. -student

A good space weather forecast begins with a thorough analysis. SEC forecasters analyze near-real-time ground- and space-based observations to assess the current state of the solar-geophysical environment (from the Sun to the Earth and points in between). Space weather forecasters also analyze the 27-day recurrent pattern of solar activity. Based on a thorough analysis of current conditions, comparing these conditions to past situations, and using numerical models similar to weather models, forecasters are able to predict space weather on times scales of hours to weeks.-NC

17. Why is forecasting space weather important?
The forecasting of space weather is critical to a variety of fields. First, it is critical to away-from-planet space missions. Beyond this, space weather has an effect on a variety of earth based electromagnetic systems, and since space weather can affect these devices, it is important to understand it. -student

Some of the specific effects of space weather on Earth systems include interference with short wave radio propagation, problems with electric power grids, the decay of satellite orbits, and radiation hazard for satellites and for astronauts during some phases of space missions.-GH

18. When do the effects of space weather show up?
Flares (sudden brightenings) affect the ionosphere immediately, with adverse effects upon communications and radio navigation (GPS and LORAN). Accompanying radio bursts from the Sun are expected to exceed cell phone system noise tolerances 2 - 3 times per solar cycle.

Solar energetic particles arrive in 20 minutes to several hours, threatening the electronics of spacecraft and unprotected astronauts, as they rise to 10,000 times the quiet background flux.

Ejected bulk plasma and its pervading magnetic field arrive in 30 - 72 hours (depending upon initial speed and deceleration) setting off a geomagnetic storm, causing currents to flow in the magnetosphere and particles to be energized. The currents cause atmospheric heating and increased drag for satellite operators; they also induce voltages and currents in long conductors at ground level, adversely affecting pipelines and electric power grids. The energetic particles cause the northern lights, as well as surface and deep dielectric charging of spacecraft; subsequent electrostatic discharge of the excess charge build-up can damage spacecraft electronics. The ionosphere departs from its normal state, due to the currents and the energetic particles, thereby adversely affecting communications and radionavigation.

Rayleigh-Taylor instability often occurs in tropical latitudes, causing rising bubbles to ascend out of the top of the ionosphere and substantially distorting the normal layering. This causes radio beams propagating through the rising columns to suffer up to 30 dB of scintillation; GPS receivers lose lock and communication signals break up as a result.-EH

19. How long have scientists known about space weather?
The effects of space weather have been known since primitive man first saw the northern lights. More recent discoveries include the solar wind. -student

Space weather is noticed mostly by its effects on Earth. After a great solar flare in 1959, telegraph operators discovered that currents from the intense aurora borealis was flowing through their systems, causing their telegraph keys to melt and stick in position. During World War II, the new invention of radar failed whenever the space weather activity was high. Comet tails that curved and pointed way from the sun showed that a solar wind, a part of space weather, was always blowing out through the solar system. When police cars in San Francisco tried to talk to their dispatchers, dispatchers in Minneapolis answered (reference: The Northern Light, A. Brekke, A. Egeland, Springer-Verlag,  New York. 1983). Plans for revisiting the Hubbell Telescope in orbit and boosting it high enough that it will not fall to Earth are driven by space weather. When space weather is high, the orbit decays more rapidly and booster missions must be flown more often.-GH

20. What is the role of the Space Environment Center?
To monitor space activity, especially the sun, in order to predict conditions caused by extraplanetary events that could have an adverse effect on earth and its various industries. -student

The role of the Space Environment Center is to gather, in real time, all the available data that describes space weather. From this, space weather forecasters form a picture of the environment from the Sun to Earth. With this information, alerts, warnings, and forecasts are prepared by Space Environment Center for users that may be affected.-GH

21. How do you monitor events on the sun?
You observe it through different filters to see different layers of the sun. Each of these layers has certain characteristic activities that signal the onset of a flare or other solar event. -student

SEC scientists and technicians utilize a variety of ground- and space-based sensors and imaging systems to view activity at various depths in the solar atmosphere. A worldwide network of USAF-sponsored optical observatories also provides space weather forecasters with detailed plain-language discussions and coded reports of activity in and around sunspot groups, as well as other areas of interest on the Sun. -NC

22. What types of industries might be impacted by space weather and how?
The communications industry has lots of problems with solar events. Solar activity can garble radio transmissions, fry the electronics on satellites and in antennas. The power industry has problems with solar events as well, as their transformers can be overloaded. Almost any industry that uses electronics in space can be affected by extremely powerful bursts, but these are rare. -student

GPS sales are projected to be $9 billion per year in 2000. GPS receivers are increasingly interwoven into the fabric of commerce and recreation.

New investment in low and mid Earth orbiting spacecraft is expected to be $30 billion by 2001. Each constellation's loss of revenue is estimated at $1 k per minute of outage per satellite; this does not consider the users' losses

Delay in assembly of International Space Station could have a domino effect on Shuttle flight manifests, at $500 M per flight.

One credible electric power outage could result in a direct loss to US Gross Domestic Product of $3 - $6 billion (reference: Barnes, P.R. and J.W. Van Dyke, "On the Vulnerability of Electric Power to Geomagnetic Storms,"  Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1990. (published as a Technical Report of the Aoak Ridge National Laboratory)).

A recent estimate is that the use of good forecasts by the power industry could save the US $365 M per year, averaged over the solar cycle (reference: "An Estimate of the Value of Geomagnetic Storm Forecasts," by Rodney F. Weiher and Thomas J. Teisberg. (Published in an economics journal.)

23. Can solar storms hurt people?
Yes. Solar storms can cause danger to astronauts, for the exposure to protons and plasma from solar storms can cause radiation poisoning. Astronauts who are not within the protection of the earth's atmosphere can be exposed to a lethal dose of radiation during a large solar storm. People flying in commercial jets at high latitudes are also exposed to higher radiation. Even people on Earth are exposed to cosmic radiation, but the amount is negligible. -student
24. Can the damage of solar storms be prevented?
Our best form of protection is the earth's atmosphere, which absorbs the majority of the effects of solar storms. In space, radiation shielding can help reduce the effects of solar storms to both astronauts and equipment. However, large storms can cause problems even within the Earth's atmosphere. Luckily, solar events can be predicted with some accuracy, so that preventative measures can be taken to reduce damage. -student
25. Is space weather "all bad" or are there some positive impacts?
In addition to causing harm, space weather also produces the aurora borealis and the aurora australis. In the future, solar weather could become a good source of energy. Space weather has the ability to cause a lot of damage, but it is not all bad. -student
26. Where can I get more information?

You can find more information on the Internet at the following sites:
Space Environment Center
SEC Education Web Page
Space Weather Sites
Space Physics Educational Sites
Solar Terrestrial Activity Report
Space Weather Report
SpaceWeather.com


Understanding Solar Phenomena

1. What satellites observe the sun that have data we can look? 2. Please explain flare classification.
Flare Classification

A flare is a sudden eruption of energy in the solar atmosphere, lasting minutes to hours, from which radiation and, sometimes, particles are emitted. Flares are classified on the basis of area at the time of maximum brightness as observed in the hydrogen-alpha wavelength (656.3 nm).

The following table shows flare importance and the associated corrected flare area in millionths of the solar hemisphere:

 
Importance 0 >10 to <100 (Subflare)
Importance 1 >100 to <250
Importance 2 >250 to <600 
Importance 3 >600 to <1200
Importance 4 >1200 
A brightness qualifier of (F) faint, (N) normal, or (B) brilliant is generally appended to the importance character.

0F would be the smallest, dimmest classification of a flare; 4B would indicate the largest, brightest classification.


The Space Environment Center also classifies flares by their x-ray intensity. X-ray flare classification is based on a flare's maximum x-ray power output (data received from the GOES satellite) according to the order of magnitude of the peak burst intensity (I), measured at Earth in the 0.1 to 0.8 NM band as follows:
 
 
Peak Flux Range (0.1-0.8 NM)
 
Classification
mks system (W m-2)
cgs system (erg cm-2 s-1)
B
I < 10-6
I < 10-3
C
10-6< I < 10-5
10-3 < I < 10-2 
M
10-5 < I < 10-4
10-2 < I < 10-1
X
10-4 < I 10-1
10-4 < I 10-1 

Five standard terms are used to describe the general level of solar activity:

 
Very Low Just < C-class x-ray events
Low C-class x-ray events 
Moderate Isolated (1 to 4) M-class x-ray events
High Several (> 5) M-class x-ray events, or isolated (1 to 4) M5 or greater x-ray events
Very High Several (> 5) M5 or greater x-ray events

Effects on Earth Systems

1. I'd like to know what impact mass coronal ejections and solar flares have on Earth's weather conditions.
The effects of flares on weather, if any, will be quite small and perhaps undetectable. It is difficult to find specific evidence of a connection between solar flares and CMEs and weather. -student

Large solar flares produce x-ray emissions. This can have an effect on minor constituents of the upper atmosphere (<60 km) such as Nitric Oxide (NO). If the conditions were to last long enough, the NO could affect middle atmospheric species such as Ozone but this is highly speculative and very unlikely. CMEs produce large changes in the magnetosphere. This will, in turn, affect the ionosphere. It is unlikely that these effects can propagate down to the lower atmospheric weather.

There is a theory that says that changes in the solar wind will affect the influx of cosmic rays. These cosmic rays might be related to cloud formation and precipitation. NASA has funded research into this area but I must emphasize that it is highly speculative and not widely accepted in the scientific community. The only person really doing this sort of research is Brian Tinsley and if you were to do a reference search on him, you would find the latest on this particular branch of research.

If there is a connection between short term solar activity and weather, it is going to be very small and difficult to measure. Furthermore, the physics behind such a connection would be highly speculative. I should think that the troposphere has a significant amount of inertia and the response times to changes in solar input would be fairly long. Flares and CMEs are short lived events and would therefore, not cause measurable changes in the weather.

There is quite a bit of evidence that changes in solar activity do have measurable affects on weather. The correlation between the temperature at specific locations and the 11 year solar cycle are sometimes quite strong. Karen Labitske in Germany has done a lot of research in this area. The physics is still highly speculative at this point though.

One reference that might be helpful is a NASA publication called Sun, Weather, and Climate by J. R. Herman and R. A. Goldberg. NASA SP-426.-RV

2. Is there a relationship between solar events and earthquakes?
The question of a solar disturbance/magnetic field change related to earthquakes has been thoroughly investigated and found to be unproven. -student

An international meeting of scientists was convened in London from November 7 to 8, 1996, on the subject of relationships of earthquakes to other phenomena for prediction purposes. Papers of that meeting appeared in the Geophysical Journal International, vol. 131, pgs. 413 to 533, 1997. (Perhaps you should read those articles and the summary by Geller). The consensus of the meeting was that prediction was not possible. As Main points out in Nature (vol 385, pg 19-20, 1997) "Modern theories of earthquakes hold that they are critical, or self-organized critical, phenomena, implying a system maintained permanently on the edge of chaos, with an inherently random element and avalanche dynamics with strong sensitivity to small stress perturbations."

Geller, a prominent seismologist at the University of Tokyo who continues to research the possible earthquake relationships to other natural phenomena, reports "The chaotic, highly nonlinear nature of the earthquake source process makes prediction and inherently unrealizable goal." If you believe that you have some solid firsthand evidence, perhaps you should write to Geller to bring yourself up-to-date on this subject (Dr. Robert, Dept. of Earth and Planetary Physics, Graduate School of Science, Tokyo University, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 JAPAN).

I have found no evidence of a significant relationship between the phenomena you talk about. Perhaps you should read my last book, "Introduction to Geomagnetic Fields" (Cambridge University Press, 1997) which discusses the realistic relationships of the solar activity to processes on Earth. --Wallace H. Campbell, whc@ngdc.noaa.gov

3.  How bright is the aurora and how can I demonstrate it?
Not an easy question to answer.  The brightness of the aurora is related to the energy flux carried by particles hitting the atmosphere.  That energy flux
is EF=(number of particles/cm2/sec)*(average energy per particle).  In the aurora the average energy per particle is about 3000 eV--that is the energy acquired by a charged particle falling through a voltage difference  of 3000 V.  The number of particles per cm2 per sec hitting the atmosphere is a typical aurora is about 2 billion per cm2 per sec.  Cast in electrical terms, this can be described in terms of an electrical current (the 2 billion particles per cm2 per sec is equivalent to a current of about 3.3 microamps per m2 - note change of units from cm to m) and, if each particle--charge carrier--had 3000 eV energy this would be a power flux of 3000*3.3*10-6 Watts/m2  = .0099 Watts per m2.

If you wanted to simulate the aurora you would have to:

1.  Build a system that would liberate about 2 billion electrons/cm2/sec from some surface.

2.  Accelerate those electrons through a 3000V potential difference (in a vacuum so that the electrons were not hitting air.

3. Pass the accelerated electrons through a thin membrane separating the vacuum from air at low pressure (say about .1 to 1% of atmospheric pressure)

4.  When the accelerated electrons hit the air, the air should emit light with many (although not all) the characteristic colors seen in the aurora.

In terms of demonstrating the physics of what goes on, a television set duplicates much of what happens in the aurora: electrons are generated from a hot filament in a TV tube, accelerated through 25000V, and hit a phosphor (rather than air) to create light.



Effects on Satellites

1. How does the "South Atlantic Anomaly" affect satellites?
The South Atlantic Anomaly is a dip in the Earth's magnetic field which allows cosmic rays, and charged particles to reach lower into the atmosphere. The anomaly is always there, but it does change in intensity. The SAA is populated with high energy particles that can penetrate the skin of the spacecraft and cause upsets in spacecraft electronics.-DS

Effects on Power Systems

1. What caused the failure of the Canadian power plant in March 1989?
On March 23, 1989, Hydro-Quebec had a 9 hour blackout affecting 9 million people. The cause was a geomagnetic induced current (GIC) due to a large geomagnetic storm.

GICs can put some transformers into what is known as half-cycle saturation, where the current in the windings can exceed the rated load for the device, and magnetic flux which is normally constrained to the transformer core can leak into adjacent structures. This can result in heating and damage to the device and adjacent structures. Note that the dramatic complete failure of a transformer does not occur very often. However, there is evidence that the lifetime of transformers in GIC susceptible regions is shorter than the lifetime of transformers in non-GIC susceptible regions. This suggests that GIC more commonly affects transformers by small amounts over time.

In addition to problems in the transformer itself, half-cycle saturation causes the transformer to draw a large exciting current which has a fundamental frequency component that lags the supply voltage by 90 degrees and leads to the transformer becoming an unexpected inductive load on the system. The large exciting current is also full of harmonics and the presence of these can lead to operation of capacitor-bank protective devices. Capacitor banks are an important device for maintaining voltage support, and the combination of a high inductive load and loss of capacitors makes voltage support difficult.

2. How could I demonstrate the effect of space weather on power systems?
For demonstration of induced currents in the electrical power grid, you could find a basic induction experiment, i.e. show that a voltage, and therefore a current, is induced in a conductor when exposed to a changing magnetic flux. The basic physics configuration one sees in textbooks is a simple loop-shaped wire through which one moves a bar magnet to induce a flow of current.--CB
3. How sensitive does a meter have to be to sense voltage in an induced current?
There is a formula to calculate the current induced in the wire but it depends on the strength of the bar magnet, the rate of change of the magnetic flux threaded through the current loop, and the resistance of the circuit. The faster you can pass the bar magnet through the loop, the stronger the current. If you have a multimeter, you might test the multimeter with a simpler circuit by hooking it up a battery and a light and seeing if you can measure current flow through the multimeter.

To get a rough idea of the voltage and current produced by magnetic induction, suppose your bar magnet has a 1 Tesla magnetic field strength, and that the area of the current loop is 100 cm2 (0.01 m2). When the bar magnet is in the loop the magnetic flux is the product of the field strength and the area. Let's suppose that the flux goes from zero to 1 Tesla x 100 cm2 in 1 second. If we use the meter-kilometer-second system of units, then the voltage would be about

E = 1 T x 0.01 m2/1 s = 0.01 Volts

For a circuit with 2 Ohms of resistance this would give a current of 0.005 Amps, (5 mA). I have used Ohm's Law that current equals voltage divided by resistance.

As you can see, the larger the circuit and the stronger the magnetic field, the larger the current. Also the faster the field changes the larger the current. As a caution, note that I assumed a uniform magnetic field throughout the current loop. In reality the field falls off as one moves away from the magnet. The closer the magnet size is to the size of the loop, the closer the uniform field approximation works. If you can get some current readings, this experiment would be one way to estimate the field strength of a typical bar magnet.--CB
 



 

Effects on Animals

1. Is it true that migratory birds are affected by space weather?
 
The NOAA Scales list animal effects starting at a G1 level, and the effects are more pronounced as the geomagnetic field is more disturbed.

It is pretty well accepted that homing pigeons and honey bees (and probably sharks and rays and various bacteria) react to the Earth's magnetic field and its variations. Quite extensive work has been done with the homing pigeons, as they are routinely released in races and can be tracked with radios (Am. Scientist, Vol. 68, May-June '80, pp.256-267). During disturbed conditions, pigeons fail to navigate home, and as a result, pigeon racers call off races if SEC forecasts these disturbances.

Honey bees apparently have been studied in terms of their "dances". The orientation of the dance (indicating direction of good forage) can be in error up to 20% in disturbed geomagnetic conditions. There are other effects--comb building, circadian rhythms--that are less well studied.


NOAA Space Weather Scales

1. What is the difference between the number of events per cycle and the days per cycle.
The number of days per cycle means the number of days on which one or more of that particular event occurred, whereas the number of events per cycle is a total count of all events. For example, we could have 7 days of minor radio blackout activity (R1) which consisted of several dozen R1 events.--CB
2. How would one find out how many of each event have occurred in the current cycle?
The National Geophysical Data Center (NGDC) has the archival responsibility for all of the events that occur during a cycle. You should be able to get some information from the NGDC web site (http://www.ngdc.noaa.gov/stp). --CB
3. At what point is a cycle considered ended and a new cycle has begun?
Traditionally the end and start of the cycle is marked by the smoothed sunspot number (you can get details about the sunspot number from the sunspot index data center http://sidc.oma.be/index.php3)--CB
4. What are the effects on mid-latitude power systems from Geomagnetic Storms?
There are two things to consider to evaluate the local interaction with any power grid. The first is a question of the local natural earth-conductivity. Areas that permit natural currents to flow are not very likely to be affected, whereas areas with poor natural conductivity provide a possible opportunity for currents to get into the grid through grounded neutrals of transformers. The other consideration is your proximity to the auroral electrojet. Under G2 conditions the aurora will have expanded somewhat, but not down to mid-latitudes. A G3 storm begins to move the aurora down to lower latitudes to the point where mid-latitude affects are possible. One complication to this is that lines of magnetic latitude do not map exactly with the geographic latitude. Thus, one tends to worry more about the East coast geographic mid-latitudes than the West coast geographic mid-latitudes because the former are closer to the magnetic pole. If you want to see a map of this, look at the relation between Kp and the aurora on our web page (/info/kp-aurora.html) --CB
5. What are the units for flux levels in Solar Radiation Storms?
"ster" stands for ster-radian, which is a unit of "solid angle." The reason that this is done used is because the instrument samples particles only over a limited angular volume. One takes the particle counts and divides by the solid angle subtended by the instrument to normalize the measurement per solid angle unit. To convert to the equivalent flux that one would expect in all directions, multiply by 4 x pi. Note that this is valid, however, only if the particle trajectories are uniformly distributed over all possible directions. --CB
6. What type of particles are measured for Solar Radiation Storms?
The particles measured are ions, mostly positive ions meaning they are atoms and molecules that have been stripped of some or all of their electrons. Ionized Hydrogen is simply a proton.
7. Do the effects of Solar Radiation Storms differ based on latitude?
Solar radiation storms are the result of energetic particles produced by solar activity. These particles have a very difficult time making it to the ground due to their interaction with the Earth's magnetic field and with the Earth's atmosphere. We hardly see anything at the ground at all, except very near to the magnetic poles. From a practical point of view, solar radiation storms are mainly a concern for spacecraft and astronauts, particularly if they are far above the stronger parts of the geomagnetic field and above the atmosphere. --CB
8. How are the three NOAA scales related?
The answer is complicated. The radio blackouts are a result of solar flares, a solar phenomena that has been known for a good 150 years or so. Solar flares are also associated with the radiation storms and can sometimes be followed by a geomagnetic storm a day or so later. However, as have learned more over the years, we have discovered some things that have modified the view:

1. The energetic particles that lead to radiation storms can be accelerated by flares or by interplanetary shocks. Interplanetary shocks occur when the Sun energetically ejects material into space, a phenomena known as a coronal mass ejection. Both types of mechanisms can contribute to energetic particles and consequently, radiation storms.

2. Geomagnetic storms are caused either by the interaction of a coronal mass ejection with the earth or by another solar phenomena called a high-speed stream, emanating from what is called a coronal hole. A coronal mass ejection is sometimes associated with a flare, but not always. As for cause and effect, it is now widely thought that the Sun's magnetic fields drive the mass ejection, rather than the radiative energy released from a flare. One often does have a coronal mass ejection that is associated with a flare, but it is not always the case. Coronal holes are regions of open coronal magnetic fields. In these voids of the sun's atmosphere, material flows rapidly away from the sun (more than it does over the closed field regions) and a high-speed stream of solar wind forms in interplanetary space. When the high speed stream interacts with the Earth we can often see a geomagnetic storm result.

3. A final complication is that geomagnetic storms end up driving the ionosphere, and can also wreak havoc on radio communications. Thus, independent of the flare effect for radio blackouts one also has radio blackouts originating from geomagnetic storms.--CB


ACE Real-Time Solar Wind

1. What is special about the ACE satellite
NASA's ACE orbits the Sun at L1, 0.99 AU from the Sun, about 1 million miles or 1.5 x 106 km or 230 Earth radii or 1 hour (+/- 20 minutes) upstream of Earth to give approximately 1 hour warning of geomagnetic storms
2. Did NOAA provide any funding for the ACE RTSW system?
Yes, NOAA provided $ 680,000 to modify the ACE satellite. We contracted with the Explorer Project, APL the spacecraft builder, and the three instrument teams. The spacecraft was modified to leave on the transmitter to continuously transmit a special subset of the data at 434 bits per second (not counting the encoding, etc.).-RZ
3. Did NOAA provide any funding for the ACE RTSW ground system put together by SEC and how does the RTSW ground system work?
No, NOAA did not provide actual dollars. We developed the ground system under the concept of a partnership, with each partner providing some contribution to the overall system. CRL in Japan provided the ground system and all the local staff at no cost to NOAA. In return for tracking ACE RTSW data in real time-the data is sent to CRL the second it is finished being processed. RAL in England is another story. They provided the ground system but we needed to pay for someone to keep it running. The USAF stepped up to this task, as part of their contribution to the program, and send us enough money each year to fund one person at RAL. So RAL is providing a lot for very little. These two stations are 100 % dedicated to tracking ACE. During the Summer they can provide nearly 23 hours of coverage, but during the Winter they can only provide about 15 hours of coverage. NASA downloads the science data once per day over a period of nearly 3.5 hours. During the download they send us the RTSW data (this was part of the NOAA-NASA agreement). No one else can track ACE when NASA is tracking, since they switch ACE to a much higher band rate for the science data dump. We also get data, on a best effort basis from the USAF AFSCN. Currently, they try to fill in any gaps in the scheduled tracking coverage. Again, this tracking is provided free to NOAA. The USAF, through their forecast center, is a partner in this program. We continue to try and expand the coverage so we can meet our goal: 96 % coverage or better every day with no gap longer than 15 minutes. Last year the CNES in France agreed to provide some limited tracking and became a partner in the program. This year we are working with ISRO in India to provide additional tracking in the early morning UTC day during the Winter months. We are also working with UCB in the hope that their new 11 m ground station will be able to track ACE. Exactly how this will work is not yet known. SEC now provides limited coverage during the midday hours under good conditions! This is the first direct NOAA contribution to the tracking partnership. Our contribution is the ingest, processing, and distribution of the RTSW data. This is not a small contribution. During the development of this ground system, we have provided staff time to help on numerous questions from all of the sites. Some software has been developed here and placed at remote sites to help in running the system.-RZ
4. What control do we have over the ACE RTSW data and over the ground system?
Although partly answered above, we set the requirements for the RTSW bit stream and it is a set mode on ACE and can not be changed. They do have more than one mode and could use one of them in place of the RTSW mode. The ACE Project considers the RTSW system a secondary payload, thus if anything goes wrong we are not first priority. However, we built the system on a non-interference basis. Thus, there is very little that we require of ACE, just keep it in the RTSW mode-434 bits per second downlink. NASA decides when they will do a maneuver, what orbit they will maintain, etc. So far they have always tried to consider our requirements when scheduling any change in the ACE satellite. The ground system is run by SEC and each partner contributes to the overall success. However, we don't pay CRL to track and at any time they could stop in theory. However, every partners has a vested interest in the success of the RTSW project and they all plan on continuing. In effect we control our own destiny, short of a complete disaster such as failure of the spacecraft or of a major instrument nothing will change. They like and want the RTSW system to work. The RTSW 'payload' on ACE generates enormous publicity, which appears to be the primary driver for much of what NASA does these days.-RZ
5. Could they send ACE off after a comet or something like they did for ISEE-3?
Very unlikely. This mission was designed from day one to monitor the Sun and has a very special payload designed to do just this one thing. It is only useful in monitoring the Sun. The same was not true for ISEE-3, which had the old fashion full cross-section of instruments (keep in mind I was on the ISEE -3 science team and still remember the discussions to send the spacecraft off in search of new missions). I can not think of any mission that is suitable for ACE, except the one it is doing presently. There have been no discussions of 'other options' at the science meetings. Ron Zwickl
6. What is the average delay time from the time the data leaves ACE until it is fully processed and into the operations center?
Our goal from the beginning of the program was to have all data processed and available in operations (and the outside world) within five minutes of the time it was broadcast from ACE. At the present time most high time resolution data are available within about 3 to 4 minutes. It is fair to ask could it be done any faster and the answer is no. The current delay is not due to processing but due to buffer sizes at ground systems and the record size of the actual data. If you are looking at longer term averaged data, such as 5 minute or 1 hour data, then just add about 5 minutes to the end of the average period to get the delay.-RZ
7. What kind of problems do we have in obtaining the goal of 96 % daily coverage with no gap larger than 15 minutes?
This is the goal that is hardest to obtain. This summer we made this goal about 4 out of 5 days. In the winter we are far from achieving this goal. There are a number of reasons for 'drop outs' in the data, from antenna coverage (not to often), to a programs locking up and not sending the data, to several types of network problems. The single biggest problem is improving our overall coverage-obtaining more ground systems. Each year we have improved and expect to continue to improve until we have complete coverage. -RZ

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