During the same period as the SRT observations, another antenna was available at Haystack, which monitored the flux at 327 MHz. This antenna was part of the monitoring for RFI for the site for the Deuterium Array being built at Haystack. The antenna was a simple dipole-like system that has a wide-angle beam. This antenna, while it was pointed straight up, picked up strong reflected signals from the sun. The data from the SRT were compared to that from the 327 MHz receiver system in order to determine whether the features seen at 327 MHz during the day were from local interference sources or from the Sun. Some strong activity seen in the 327 MHz data is related to local thunderstorms.
The plots also include x-ray data from the GOES-8 satellite (http://www.sec.noaa.gov) that are 1-minute averages in the 0.1-0.8 nm range.
The data were read into Microsoft Excel and averaged and plotted. The plots do not
include calibrated SRT and 327 MHz data. The SRT data are raw antenna temperature numbers
while the 327 MHz and the x-ray data have been arbitrarily scaled so that they fit on the same plot for comparison purposes.
The slight discontinuities in the SRT intensities are caused by pointing drifts.
The Plots:
Day 184 - 07/03/02- possible x-ray, SRT correlation at 20:30 UT
Day 187 - 07/06/02- 327, SRT correlation
Day 188 - 07/07/02
Day 189 - 07/08/02
Day 190 - 07/09/02- SRT event, no obvious x-ray correlation
Day 192 - 07/11/02- SRT, x-ray correlation at ~14:45 UT
Day 193 - 07/12/02
Day 195 - 07/14/02- intense x-ray activity, no obvious correlation
Day 196 - 07/15/02- x-ray, SRT and 327 event
Day 197 - 07/16/02- xray, SRT and 327 event
Day 198 - 07/17/02- x-ray, SRT event
Day 199 - 07/18/02- SRT, 327 event, possible correlation with weak x-ray event
Day 200 - 07/19/02- 327, SRT event
Day 201 - 07/20/02
Day 202 - 07/21/02- activity in 327 from thunderstorms
Interpretation:
Radio emission at meter-wavelength (m-l) and decimeter-wavelength (dm-l)
from flares is quite different from emissions at centimeter and millimeter wavelengths.
This has to do with the fact that at the shorter wavelengths the emission is caused
by incoherent gyrosynchrotron radiation mechanisms while at the longer wavelengths
the emission comes from coherent plasma radiation. The 1-3 GHz frequency range appears
to lie at the transition between the two types of emission mechanisms. The shorter
wavelength radio flares correlate well with the x-ray events while the longer wavelength
events appear not to be well correlated. This lack of correlation also points to the
different heights in the solar atmosphere at which the various events occur.
Solar flare emissions at X-ray wavelengths are sometimes accompanied by
Coronal Mass Ejections (CMEs), which move away from the Sun at speeds
exceeding 1000 km/s carrying strong magnetic fields and energetic
particles. If Earth-directed, these CME events can couple significant
amounts of energy into Earth's charged upper atmosphere and trigger
geomagnetic storms. These storms have large impacts on atmospheric
dynamics, and can also cause auroral displays, satellite outages, power
grid disruptions, and GPS navigation errors. The SRT provides a tool
for students to detect some of these solar flare events and to motivate their study of the
Sun's effects on Earth's atmosphere.
References for further reading:
