Tracking Space Weather at the Arecibo Observatory

Astronomy

Space weather describes variations in the space environment between the Sun and the Earth. Large-scale magnetic disruptions on the Sun can result in Coronal Mass Ejections (CMEs) and solar flares that can direct a significant amount of energetic particles toward Earth. The resulting distortions of the Earth’s magnetosphere - geomagnetic storms - have the potential to disrupt, degrade, and permanently destroy spacecraft including GPS and communication satellites.

It has therefore become increasingly important that we understand the behaviors of the Sun and become capable of forecasting space weather events.

At the Arecibo Observatory (AO), the upgraded 12-meter telescope and the newly-installed Callisto solar radio spectrometer are actively observing the Sun and regularly detecting space weather events. These radio-band observations are contributing unique pieces to the many outstanding puzzles about the Sun’s activity and its effect on Earth.

Solar Mapping with the 12-m: Since its upgrade in December of 2021, the 12-meter telescope at AO has been used to create daily maps of the Sun in the frequency range of 8.1 - 9.3 GHz. The regular monitoring of the solar emission observed at 8.6 GHz clearly detects the magnetically active regions on the Sun that are capable of producing space weather events, including intense solar flares and energetic CMEs.

The 12-m has regularly detected strong radio emissions from the Sun that correspond with increased emission captured at other wavelengths by NASA facilities like the Solar Dynamics Observatory and the GOES-16 space missions. This indicates that continued monitoring of the Sun in the radio will be incredibly useful for identifying and predicting the development of active regions capable of producing space weather events.

Interplanetary Scintillation: The remote-sensing technique called “Interplanetary Scintillation” can be extremely useful for getting the 3-D view of solar storms and coronal mass ejections. Interplanetary scintillation (IPS) detects the “radio twinkling” of compact radio sources caused by the solar wind. The upgraded 12-m radio telescope will observe IPS on a number of radio sources and these observations can probe CMEs at regions inaccessible to spacecraft. Observations and analysis tools developed by Dr. P.K. Manohoran, a research scientist at the Arecibo Observatory, have been used to develop IPS-based model(s) to predict the arrival of Coronal Mass Ejections as well as infer the ambient solar wind distribution in the inner heliosphere.

Space Weather Events with the AO Callisto: Since its installation at AO in October of 2021, the AO Callisto solar radio spectrometer has detected numerous space weather events. The AO Callisto is one of the most active e-CALLISTO radio spectrometers that make up an international network of telescopes (see Figure 1). The Callisto instrument operates from 15 - 100 MHz and continually observes the Sun from 6 AM - 6 PM AST, with new data being uploaded to the e-Callisto site every 15 minutes. At these frequencies, the e-Callisto network is measuring radiation caused by electron beams, shocks, possibly trapped electrons, and high-frequency waves in the plasma emitted by the Sun during events.

Figure 1: Plot from the e-CALLISTO solar spectrometer site that shows various locations of the e-Callisto radio spectrometers and the number of solar radio bursts observed in the month of April. The network allows 24 hour monitoring of the Sun. The AO Callisto routinely captures some of the highest number of solar radio bursts events each month.

Large Coronal Mass Ejection Detection with AO Callisto: On July 16th, 2022, the Callisto spectrometer recorded reverve bursts associated with a large Coronal Mass Ejection. The bursts are signatures of electron beams traveling along closed magnetic loops and are likely the first detections of such bursts using the AO spectrometer. NASA’s Solar Dynamic Observatory (SDO) and STEREO missions, which are space-based telescopes, captured images of the CME at the near-Sun region, as can be seen in the images in Figure 2.

Figure 2: (Right) The Arecibo Observatory captured an intense radio burst on the 16th of July using the CALLISTO radio spectrometer. (Left) Two space-based NASA telescopes simultaneously imaged a large Coronal Mass Ejection from the Sun.

Independence Day Solar Flare: While the U.S. celebrated their Independence Day, the Sun was setting off some fireworks of its own. An X-ray flare from the Sun was detected by the AO Callisto spectrometer. Follow-up observations using the 12-meter telescope show the region of the Sun where the flare originated from. Although this flare was a moderate event, it was well-recorded by both the Callisto spectrometer and the 12-m telescope, showing how sensitive both instruments are for detecting and developing accurate forecasting of space weather events.

Figure 3: The Arecibo Observatory captured a solar flare event on the 4th of July 2022. The image on the left shows the signal collected from the Sun by the 12-m radio telescope at 8647 MHz. The bright spot seen in the radio image from the 12-m telescope (the green arrow) corresponds with where an X-ray flare had been detected by other telescopes. In the center, there is an image collected by the NASA Solar Dynamics Observatory (SDO). It similarly shows activity in the same region detected by the 12-m telescope. On the right, the spectrum shows high intensity signal that was captured by the CALLISTO radio spectrometer at Arecibo corresponding with the time of the solar flare.

The Arecibo Observatory is well-primed to perform observations of the Sun, contributing to our better understanding and forecasting of Space Weather. The team of scientists and engineers involved in these projects include: P K Manoharan, Christiano Brum, Phil Perillat, Alfredo Santoni, and Felix Fernandez.

Keywords: 12-m Antenna; Callisto; space weather