Earth's ionosphere reacts strongly to the intense x-ray and ultraviolet radiation released by the Sun during a solar event. By using a receiver to monitor the signal strength from distant VLF transmitters, and noting unusual changes as the waves bounce off the ionosphere, students around the world can directly monitor and track these Sudden Ionospheric Disturbances (SIDs).

Stanford's Solar Center, in conjunction with the Electrical Engineering Department’s Very Low Frequency group and local educators, have developed inexpensive SID monitors that students can install and use at their local high schools. Students "buy in" to the project by building their own antenna, a simple structure costing less than $10 and taking a couple hours to assemble. Data collection and analysis is handled by a local PC, which need not be fast or elaborate. Stanford will be providing a centralized data repository and chat site where students can exchange and discuss data.

Because there are VLF transmitters scattered around the world, the monitors can be placed virtually anywhere there is access to power.

For more information, see solar-center.stanford.edu/SID

List of Partners

Stanford Solar Center Deborah Scherrer Hao Thai Sharad Khana Scott Winegarden Paul MortfieldStanford Solar Observatories Group Philip Scherrer Sarah GregoryStanford EE Department Umran Inan Morris Cohen Justin TanCal State University Hayward Ray Mitchell, Chief EngineerChabot Community College Shannon Lee Tim DaveSan Lorenzo High School William Clark Richard StynerCastro Valley High School Sean Fotrell Kenny Oslund (now at CalTech)

Connecting the Earth to the Sun: Students Monitor Solar Disturbances to Earth‘s Ionosphere

Deborah Scherrer, Ray Mitchell, Morris CohenStanford University

The Sun, Earth’s Ionosphere, and VLF Radio

waves

Source: http://www.cmsstudios.com/fly2k/99flights/images/ebbyjm.jpg

200’ Towers

Antenna Wires

One of ~24 VLF broadcasting stations around the world --, Jim Creek, WA “NLK” 24.8KHz

1 Cycle = 7.5 Miles (12 KM)

Amplitude (Peak-to-Peak) for 24.8KHz

Distance traveled over time

Rad

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An education project to build and distribute inexpensive ionospheric monitors to students around the world. Two

versions of the monitor exist – one low-cost and one research quality.

AtmosphericWeatherEducationalSystem forObservation andModeling ofEffects

B-Field Antenna

Preamp Long Cable

Line Receiver

Analog to Digital

Computer

GPS Antenna

•Designed to capture ELF/VLF frequencies, roughly 30 Hz-50kHz•Dual use system -- Daytime: monitor solar activity Nighttime: monitor atmospheric phenomena, e.g. lightning •Precision timing/phase accuracy•So sensitive that nearly any signal above the ambient Earth noise floor can be detected•Broadband•Easy to build, set up, use, and repair•Data appropriate for high school as well as solar and ionospheric researchers•Low cost (~$1700 per monitor)

B-Field, Magnetic LoopB-Field, Magnetic LoopOrthogonal PairOrthogonal Pair1.0 1.0 ΩΩ, 1.0 mH, 1.0 mHVarious sizes okVarious sizes okCuts off at ~318 HzCuts off at ~318 Hz

Preamp impedance matchedPreamp impedance matchedPaschal amplifierPaschal amplifier3 cutoff modes3 cutoff modesGain selectableGain selectableCalibration circuitCalibration circuitWeatherproofWeatherproof

PowerOne Had15 power supplyPowerOne Had15 power supplyAnti-aliasing filterAnti-aliasing filterGPS synchronizationGPS synchronization

LTC1562LTC156212th order lowpass12th order lowpassElliptical filterElliptical filter47 kHz cutoff47 kHz cutoff100dB attenuation at 55 kHz100dB attenuation at 55 kHz50 us relative delay50 us relative delay

Motorola M12+ OnCore GPSMotorola M12+ OnCore GPSAnd FPGA provide 1 pulse And FPGA provide 1 pulse per second signal with 200 per second signal with 200 ns accuracyns accuracy

National Instruments 6034ENational Instruments 6034EPlugs into PCI slotPlugs into PCI slotPCMCIA laptop version PCMCIA laptop version availableavailable200 kS/second, 16-bit200 kS/second, 16-bit100 kHz sampling each channel100 kHz sampling each channel

Two channel: Two channel: Narrowband & broadbandNarrowband & broadbandWorks in conjunction with MatlabWorks in conjunction with Matlab

AWESOME -- The Research Quality MonitorAWESOME -- The Research Quality MonitorSID – The low-cost monitorSID – The low-cost monitor

SuddenIonosphericDisturbance monitor

Pre-Amp

24.8KHzFilter

SignalStrength

DATAQ ComputerRS-232

Coax

=

All frequencies

Band-pass, Only 24.8KHz(Amplitude Modulation)

DC voltageLevel

10 bit, Analog to DigitalConversion

Sample every5 Seconds

•Preassembled and pretuned•Students build their own, simple antennas•Data handled and plotted by Excel•Changeable frequency boards tuned to particular VLF transmitters around the world •Easy to set up and use•Suitable for use in high school and community colleges•Low cost (~$100 per monitor)

SID box before silkscreening

#Event Begin Max End Obs Q Type Loc/Frq Particulars Reg##-------------------------------------------------------------------------------1960 + 1727 1736 1744 G12 5 XRA 1-8A C4.5 3.1E-03 04241990 + 1930 1946 1954 G12 5 XRA 1-8A C5.9 5.9E-03 04242000 + 2112 2134 2140 G12 5 XRA 1-8A C3.8 3.1E-03 04242040 + 2341 2354 0002 G12 5 XRA 1-8A M1.3 8.5E-03 0424

Detecting Flares with SID

C4.5C5.9

C3.8M1.3

:Product: 20030802events.txt:Created: 2003 Aug 05 0302 UT:Date: 2003 08 02# Prepared by the U.S. Dept. of Commerce, NOAA, Space Environment Center.# Please send comments and suggestions to sec@sec.noaa.gov ## Missing data: ////# Updated every 30 minutes.# Edited Events for 2003 Aug 02##Event Begin Max End Obs Q Type Loc/Frq Particulars Reg##-------------------------------------------------------------------------------1910 + 1529 1537 1545 G12 5 XRA 1-8A B8.1 6.3E-04 04241910 1533 1534 1553 HOL 3 FLA S17E71 SF 04241920 1604 1609 1617 HOL 3 FLA S18E70 SF 04241930 1625 1650 1726 HOL 3 FLA S18E68 SF 04241930 + 1637 1642 1650 G12 5 XRA 1-8A C1.1 7.6E-04 0424

Interpreting SID DataInterpreting SID Data

SID Events!

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Local Nighttime DaytimeSunrise Local Nighttime

C4.5C5.9

C3.8M1.3

The students receive their SID data as a signal strength value and a timestamp. The data are easily read by Excel and graphed. There is a characteristic sunrise and sunset shape to the graph, which can be used to test the monitor. Solar events show up as spikes in the signal strength. Students compare their spikes to data from the GOES satellite to identify flares. Occasionally, students will detect flares that the (human) GOES data interpreter have missed! Students can also track down the solar active region which generated the disturbance.

Students also pick up other signals, which could be from Gamma Ray Repeaters, lightning storms, or even local interference. By talking with each other and checking other data, they attempt to determine what caused their unidentified signals.

Stuents CompareTheir Data with that from GOES

Students Locate Source of Disturbance

VERY LOW FREQUENCY (VLF) Radio Transmission Stations

Note – VLF signals can be received all over the world, whether there is a station nearby or not!

Station Station Frequency Radiated Site ID (kHz) Power (kW) U.S. Navy Cutler, ME NAA 24.0 1000 Jim Creek, WA NLK 24.8 250 Lualualei, HI NPM 21.4 566 LaMoure, ND NML 25.2 500 Aquada, Puerto Rico NAU 40.8 100 Keflavik, Iceland NRK 37.5 100Australia Harold E. Holt NWC 19.8 1000Federal Republic of Germany Rhauderfehn - 18.5 500 Burlage DHO 23.4 - France Rosnay HWU 15.1 400 St. Assie FTA 16.8 23 LeBlanc HWU 18.3 -Iceland Keflavic TFK 37.5 - Italy Tavolara ICV 20.27 43 Norway Noviken JXN 16.4 45 Russia Arkhanghelsk UGE 19.7 150 input Batumi UVA 14.6 100 input Kaliningrad UGKZ 30.3 100 input Matotchkinchar UFQE 18.1 100 input Vladivostok UIK 15.0 100 input Turkey Bafa TBB 26.7 United Kingdom Anthorn GQD 19.0 500 Rugby GBR 16.0 45 London GYA 21.37 120

All information courtesy of Bill Hopkins, Technical Representative for Pacific-Sierra Research Corp.

Stanford Solar Observatories Group