Abstract Details
| Name: Hariharan Krishnan Affiliation: Indian Institute of Astrophysics Conference ID: ASI2015_423 Title : AN ESTIMATE OF THE CORONAL MAGNETIC FIELD NEAR A SOLAR CORONAL MASS EJECTION FROM LOW-FREQUENCY RADIO OBSERVATIONS Authors and Co-Authors : Ramesh R.(1), Kishore P.(1), Kathiravan C.(1) and Gopalswamy N.(2) (1) Indian Institute of Astrophysics (2) Solar Physics Laboratory NASA/GSFC Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : The Indian Institute of Astrophysics presently operates three different instruments, a radio heliograph (GRAPH), a low frequency radio spectrograph (GLOSS) and a radio polarimeter (GRIP) at the Gauribidanur radio observatory about 100 km north of Bangalore. All the above instruments are deidicated for solar observations and operate in the frequency range 120 – 40 MHz which corresponds to a heliocentric distance range of 1.2 – 1.8 R 0 in the solar atmosphere. The above is presently inaccessible to other regions of the electromagnetic spectum due to practical difficulties. We report observations, obtained with the above instruments, of a type II solar radio burst associated with a solar coronal mass ejection (CME) that occurred on 2013, May, 02. The burst was associated with a 1N class Hα flare and M1.1 class GOES soft X-ray flare from AR 11731 located at the heliograghic coordinates N10W25. The spectral observations indicate that the burst has fundamental (F) and harmonic (H) emission components with split-band and herringbone structures. The imaging observations at 80 MHz indicate that the H component of the burst was located close to the leading edge (LE) of the CME. Using the polarimeter observations of the type II burst, also at 80 MHz, the magnetic field in the coronal region ahead of and behind the associated MHD shock front were estimated to be ~ 0.7-1.4 +/- 0.2 G and ~ 1.4-2.8 +/- 0.1 G, respectively. Routine measurements of the magnetic field strength in the solar atmosphere are presently limited to the photospheric and chromospheric layers of the sun. The coronal magnetic field is estimated from such measurements using extrapolation techniques. Also estimates of magnetic field close to the LE of a CME are rarely reported. Given the paucity of coronal magnetic field measurements at present, particularly in close temporal and spatial association with a CME, our results provide useful constraints on the magnetic field strength involved in shock acceleration theories. |