The 14 July 2000 meter-wavelength dynamic radio spectrum

To a special Solar Physics issue on the Bastille Day Event:
Materials for the accompanying CD-ROM

Multi-scale temporal features of the 14 July 2000 meter-wavelength dynamic radio spectrum compared with TRACE data

by I.M. Chertok, V.V. Fomichev, A.A. Gnezdilov, R.V. Gorgutsa, V.V. Grechnev, A.K. Markeev, R.W. Nightingale, and D.E. Sobolev

Figure 1 (100 KB). SOHO/EIT (a) and LASCO/C2 (b) images show the region of the eruptive flare event of 14 July 2000 and related halo CME. The compressed inverted IZMIRAN dynamic radio spectrum in 05:50-13:00 UT interval (c) and extracted time-intensity profiles (d) at 58 MHz (right axis) and 86 MHz (left axis) display large-scale restructuring of the noise storm associated with the event: sharp weakening of the pre-existing noise storm in the 75-100 MHz range and some intensification of radio emission at lower frequencies. This phenomenon was perhaps caused by interaction of the halo CME with emitting coronal structures.

Figure 2 (47 KB). Inverted TRACE images at 195 Å illustrating development of the EUV post-eruption arcade with the well-organized loop, two-ribbon, and spine structures (see the movie indicated below). Note that the exposures have been rescaled to the same peak intensity to show the evolution of the bright elements. The field of view is 230 by 170 Mm.

Figure 3 (115 KB). Medium-scale dynamic spectrum (a), 204 MHz metric (b) and 3000 MHz microwave (c) profiles of the "Bastille Day" event. Several type II bands and slow-drifting decimetric continuum are marked by indexes (aa)-(dd) and (ee), respectively. The frequency drifts of the clearest bands correspond to the estimated shock wave speed of 1100-2300 km/s that is comparable with the observed CME speed. Significant broadband enhancements of the metric radio emission took place around of 10:24-10:27 UT coinciding with sharp development of the EUV arcade in the north-east direction (see the movie indicated below). It appears to correspond to the intensification of the electron acceleration in a process of post-eruption loop formation.

Figure 4 (75 KB). Enlarged dynamic spectrum of the initial phase of the event with type II bands (aa)-(dd) and some other fine-structure elements.

Figure 5 (115 KB). Enlarged fragments of the dynamic spectrum revealing the radio pulsations and type III-like bursts. At the initial and maximum phases, these features have a time scale of a few seconds which coincides with a typical time of formation and brightening up of the loops in the EUV arcade. These the second-scale radio pulsations appear to be related to the temporal fragmentation of the post-eruption magnetic reconnection and particle acceleration processes. As for the longer ten-second-scale pulsations predominating at the end of the flare event, they may have been exited particularly by MHD oscillations of higher and bigger coronal loop-like flux tubes, perhaps somehow related to the CME.

Movie: This composite movie allows to compare development of the IZMIRAN metric-wavelenght dynamic spectrum and the EUV post-eruption arcade observed with TRACE at 195 Å: