ALMOST-X FLARE AND CME: This morning, Jan. 23rd around 0359 UT, big sunspot 1402 erupted, producing a long-duration M9-class solar flare. The explosion's M9-ranking puts it on the threshold of being an X-flare, the most powerful kind. NASA's Solar Dynamics Observatory captured the flare's extreme ultraviolet flash:
The Solar and Heliosphere Observatory (SOHO) and the STEREO-Behind spacecraft have both detected a CME rapidly emerging from the blast site. Analysts at the Goddard Space Weather Lab estimate a velocity of 2200 km. There is little doubt that the cloud is heading in the general direction of Earth. A preliminary inspection of SOHO/STEREO imagery suggests that the CME will deliver a strong glancing blow to Earth's magnetic field on Jan. 24-25 as it sails mostly north of our planet. Stay tuned for updates.Solar flare alerts: text, voice.
JAN. 22ND CME IMPACT: Arriving a little later than expected, a coronal mass ejection (CME) hit Earth's magnetic field at 0617 UT on Jan. 22nd. According to analysts at the Goddard Space Weather Lab, the CME strongly compressed Earth's magnetic field and briefly exposed satellites in geosynchronous orbit to solar wind plasma. For the next 24 hours, Earth's magnetic field reverberated from the impact, stirring bright auroras around the Arctic Circle. Bjørn Jørgensen observed this display from Tromsø, Norway:
"This was amazing," he says. "It was a wonderful experience to see these stunning auroras."
NOAA forecasters estimate a 10% - 25% chance of continued geomagnetic storms tonight as effects from the CME impact subside. The odds will increase again on Jan. 24-25 as a new CME (from today's M9-clare) approaches Earth. High-latitude sky watchers should remain alert for auroras. Aurora alerts: text, voice.
The Jan. 22nd CME also disturbed Earth's ionosphere. In Atlanta, Georgia, radio engineer Pieter Ibelings monitored a 4.5 MHz CODAR (coastal radar) signal as it bounced off layers of ionization along the US east coast. "The moment of impact can be clearly seen on the CODAR radar plot," he points out:
"The CODAR transmitters are located all around the coast and are used for mapping the ocean currents to a distance of about 200 miles," Ibelings explains. "These signals also propagate through the ionosphere so they can be picked up all around the world. The signals are almost perfect for ionospheric sounding since they are linear chirps. I capture the chirp with a receiver locked to GPS both in frequency and time. I then de-chirp the waveform so I can extract the time of arrival information at my location."
The CODAR echoes show ionization layers shifting vertical position by some hundreds of kilometers, changes that surely affected the propagation of HF radio signals in the aftermath of the impact. More information about Ibelings' observations may be found here.
