The Post-Coronal Mass Ejection Solar Atmosphere and Radio Noise Storm Activity

Abstract

We carried out a statistical study of solar radio noise storms whose onset was in the aftermath of coronal mass ejections (CMEs) that occurred during 1997-2004, the first half of present solar cycle 23. The work is an attempt to understand the post-CME corona through observations of noise storms since the latter are considered to be closely related to structural changes there. The radio events were taken as the starting point for our study, and details about start time and location were available for 340 of them. We imposed the following conditions to verify the association between the above two phenomena: (1) the noise storm must have occurred ≤24 hr from the onset of a CME and (2) the central position angle of the CME must be located inside an angular span of ‫54ע‬Њ with respect to the noise storm. We found that 196/340 noise storms were associated with CMEs. More interestingly, the time interval between CME liftoff and noise storm onset in all the above cases was ≤13 hr. We suggest that this represents the upper bound of the timescale over which coronal magnetic field reorganization had taken place in the aftermath of the aforementioned 196 noise storm associated CMEs. We also found that for a particular CME, the above temporal cutoff depends on its kinetic energy. Overall, it varies inversely with the logarithm of CME kinetic energy.

An Estimate of the Magnetic Field Strength Associated With a Solar Coronal Mass Ejection From Low Frequency Radio Observations

“…We would like to mention here -8that no GRAPH observations were available during the type IVm burst in Figure 1. The discrete source close to the limb in the north east quadrant in Figure 4 is presumably weak non-thermal radio noise storm activity often observed near the location of a CME in its aftermath (Kerdraon et al 1983;Kathiravan et al 2007). The peak T b of the source is…”

A Weak Coronal Heating Event Associated with Periodic Particle Acceleration Episodes

“…Most of the noise storms were associated with flaring events, and were interpreted as nonthermal emission triggered by flare-accelerated electrons (e.g. Dodson 1958;Le Squeren 1964;Willson et al 1998;Kathiravan et al 2007;Iwai et al 2011). Some of these bursts also show quasi-periodic brightness fluctuations ranging from a few seconds to minutes in their light curves (e.g.…”

High Dynamic Range Observations of Solar Coronal Transients at Low Radio Frequencies With a Spectro-Correlator

“…The applicability of the above arguments to the present case is further strengthened by the reports that there is large-scale reconfiguration of the coronal magnetic field (which facilitates reconnection) in the aftermath of a "halo" CME. The time period over which this occurs is 19 hr (Hansen et al 1974;Hiei et al 1993;Kathiravan et al 2007). Figure 4.…”