Hercules A

Hercules A
Radio-Optical View of the Galaxy Hercules A - Many thanks to: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Tuesday, May 31, 2011

Solar activity on 110529

The illustration shows a complex event lasting for about 3 hours at Nancay, near midday.
Late in the day, STEREO WAVES B recorded another long period of strong bursting.

Friday, May 27, 2011

Io-A on 110522

Below the spectrum, I show a small air view of the Nancay Decametric Array in Central France. It has 144 conic logarithmic spirals, 72 per polarization, in a 12x12 square array. The axis of each cone is tilted south at 70 degrees altitude, for better coverage of the Sun and Jupiter.

Most days the Sun is observed between about 8 to 16 UT. Jupiter is observed for about 10 months of the year, mostly at night.
The Archive has close to 20 years of data.

Maximum gain 25 dB
Area ~ 8000 m^2
Bandwith 10 to 120 MHz
8 copper coated steel wires connected to the coax by diode switches
Only 6 wires are used at any given time, 2 opposite wires are left disconnected
By adjusting the diode switches, the phasing can be changed in steps of 45 deg
There are also delay lines
Sensitivity 100 Jy

My thanks to Paris Observatory.

Monday, May 23, 2011

Correlation of type III, electron spike, and ultraviolet jet events on 100222

Klassen with Gomez-Herrero and Heber, 2011:
study STEREO A data from the WAVES radio telescope, the SEPT solar electron proton telescope, and SECCHI EUV images.

I quote from the abstract:
"...Each of the four events was associated with a type III radio burst and a narrow EUV jet. All the events show nearly symmetric "spike"-like time profiles with very short durations ~ 5 min. The estimated electron injection time for each individual event shows a small time delay between the electron spike and the corresponding type III radio emission and a close coincidence with an EUV jet. These observations reveal the existence of spike-like electron events showing nearly "scatter-free" propagation from the Sun to STEREO-A. From the time coincidence we infer that the mildly relativistic electrons are accelerated at the same time and at the same location as the accompanying type III emitting electrons and coronal EUV jets. The characteristics of the spikes reflect the injection and acceleration profiles in the corona rather than interplanetary propagation effects..."

This is the summary of their main results:

i) A sequence of four spikes occur during a short time interval of 100 min and show almost symmetric time profiles with durations below 5 min.

ii) All electron spikes were temporally coincident with type III radio bursts and very collimated recurrent EUV coronal jets, appearing at the same location and showing the same trajectory.

iii) The sharp spike-like profiles and the observed durations between three and five minutes set an upper limit on the duration of the electron injection into the interplanetary medium of ≤1 min, comparable with the durations of type III radio bursts.

The illustration shows figures 1 and 2 from the paper.

Tuesday, May 17, 2011

Localization of a type III event on 071231

Thejappa and MacDowall 2010:
have studied the trajectory of the radiating region for this event, probably associated with a C8.3 flare.

Over the 16 MHz to 40 kHz band, assuming the frequencies correspond to the electron plasma frequencies, the radiation corresponds to heliocentric distances from about 1 Rsun to 1 AU.

The illustration shows details of the STEREO WAVES spectra and figures 1 and 14 from the paper.

More to follow on the interesting ray tracing methods used in this study.

Friday, May 13, 2011

Type III followed by II on 110511; CME on 110509

Two wonderful days for Solar study !!

Culgoora recorded a beautiful type II burst in the 18 to 57 + MHz band. STEREO WAVES A recorded part of it, just below 16 MHz.

A Coronal Mass Ejection powered the type II radiation observed on 110509. The illustration shows details of the CME and the associated C5.2 flare near the East limb.

Monday, May 9, 2011

Beautiful Solar type II and III radio emission

This Solar burst was recorded by the Culgoora Observatory in Australia, in the 18 to 57 plus MHz band, and the STEREO WAVES Beacon data, below 16 MHz.

The space based STEREO A and B observatories also recorded type II radiation (slow negative frequency drift) near 2 MHz, following a type III burst (fast negative frequency drift).

My thanks to the Culgoora and STEREO Observatory Teams. The spectra they publish is a wonderful complement to the charts recorded (at much higher time resolution) with Radio JOVE Educational Program Kits. I greatly enjoy studying all the data, it helps me to better understand the great complexity of Solar radio events.

I hope to study more detailed STEREO spectra in a few days, once the higher resolution data is downloaded from the spacecraft.

The image includes a chart with the positions of the Earth, the STEREO Observatories, and planets Mercury and Venus.

Mercury, Venus, and Jupiter are currently in a lovely conjunction, as seen from the Earth at dawn.