IHYUNBSS Initiative

1
IHY/UNBSS Initiative
VLF Remote Sensing of the Lower Ionosphere
Solar Flares, Electron Precipitation, Sprites,
and Giant g-ray Flares 1U S Inan, 1M Cohen 2P
H Scherrer, 2D Scherrer 1Space,
Telecommunications and Radioscience Laboratory
Stanford University, Stanford, California
94305 http//www-star.stanford.edu/vlf/ 2Hansen
Experimental Physics Laboratories Stanford
University, Stanford, California
94305 http//sun.stanford.edu/
2
Subionospheric VLF Remote Sensing
3
VLF Detection of Solar Flares
from Ray Mitchell
4
VLF Signatures of Gravity Waves
5
(No Transcript)
6
VLF Detection of Lightning-Induced Electron
Precipitation
7
Holographic Imaging of the Lower Ionosphere
VLF receivers at 13 high schools Provides
excellent opportunities for outreach
8
Subionospheric VLF Signatures of LEP Events
VLF Amplitude Data for 24 March 2001
Theoretical Precipitation Region
The HAIL array captures the full latitudinal
extent of the LEP events.
9
New HAIL Network
10
VLF Sensing of Ionospheric Disturbances over
Europe
11
Sprites Above Thunderstorms
12
Elve Observed from Space
13
Sprites and Early/fast VLF Events Haldoupis et
al., 2005
14
Disturbance of the Nighttime Ionosphere by SGR
190014
15
Repeated Disturbance of the Ionosphere by SGR
190014
16
VLF Detection of the Disturbance of the Daytime
Lower Ionosphere

• Very large amplitude/phase perturbations on VLF
  signals, the great-circle propagation paths of
  which are illuminated by the Flare
• Flare center very near the sun ionosphere
  day-lit

17
VLF Observations as Educational Outreach

• CISM Educational Outreach
• Professor Phil Scherrer
• High School Outreach
• Low Cost
• Easy to Use
• Dual use system
• Daytime monitor solar activity (x-ray flares)
• Nighttime monitor lightning-induced electron
  precipitation, gravity waves, sprites, etc.
• Science grade measurement, in terms of
  resolution, sensitivity, timing, and dynamic
  range

18
Antenna, Preamp Line Receiver
19
Computer, Line Receiver A/D Card

• National Instruments 6034E
• Plugs into PCI slot PCMCIA laptop version
  available
• 200 kS/second, 16-bit 100 kHz sampling each
  channel

20
Typical System Setup (Inside)
21
ELF/VLF Preamplifier Line Receiver
22
ELF/VLF Line Receiver Guts 12-pole AAF

• LTC1562 12th order low-pass
• Elliptical filter with 47 kHz cutoff
• 90dB attenuation by 55 kHz lt50us group delay

23
GPS Antenna/Card Dummy Loop for Calibration

• Motorola M12 OnCore 1 pps 200 ns
• FPGA gives 100 kpps lt100 ns drift
• Phase error lt 2.7 at 25 kHz

24
Small Triangular Antenna and Preamplifier
25
Stanford VLF Receiver now in Calcutta, India
Dr. Sandip Kumar Chakrabarti
26
Stanford Receivers in Dublin Tunis Join
European VLF Network
Drs. Peter Gallagher, Hassen Ghalila
27
Summary

• Subionospheric VLF observations allow the
  measurement of the D-region of the lower
  ionosphere, normally not accessible with other
  instruments
• New low-cost-yet-science-grade instruments allow
  multiple point (distributed arrays) measurements
  on a global scale, with participation on the part
  of host institutions, by having access to all
  data from all sites
• The menagerie of phenomena involved, as well as
  the rich and highly variable nature of data
  (especially nighttime) fosters real educational
  outreach opportunities, with lots to do for all
  participants