This award funded a major upgrade of the Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA). Through installation of new antennas, together with a dense network of optical fiber and power cables, the OVRO-LWA was upgraded to 352 antennas spread across a 2.4 km diameter area. Signals from every antenna are brought together, digitized and combined, producing a very high volume data stream of 1 Tbit/sec. Making use of newly upgraded analog and digital electronics, including FPGAs and GPUs, these data are combined to image the entire sky every few seconds at the longest wavelengths (lowest frequencies) accessible from the Earth. This all-sky imaging capability is uniquely powerful worldwide and enables a broad range of science.

The Magnetospheres and Space Weather Environment of Exoplanets:

The OVRO-LWA will make use of all-sky images with 10-second time resolution for near-continuous monitoring of the nearest 4000 known stellar/planetary systems to search for magnetospheric radio emission from exoplanets, offering the best avenue towards measuring the magnetic fields of exoplanets for the first time. The same data will be searched for the transient radio signatures of coronal mass ejections (CMEs) and the analogs of solar energetic particle (SEP) events. These events may play a key role in modifying the atmospheres of planets orbiting active stars, including the young Sun, but are poorly constrained for stars other than the Sun.

Cosmic Dawn

Cosmic Dawn is the era when the first stars and galaxies formed.    It was about 250 million years after the Big Bang – or about 13.5 billion years ago.  So far astronomers have very few observations of this era. With OVRO-LWA, we will look for the signature of neutral hydrogen in the gas between the first galaxies during Cosmic Dawn. The primary challenge for detecting the Cosmic Dawn signal is separating it from other astronomical radio sources in the foreground.  There are many strong sources of radio waves in the sky.  Our own Milky Way galaxy is the dominant radio emitter seen from Earth.  It emits radio waves primarily through synchrotron radiation, which is created by electrons moving at relativistic speeds around magnetic fields in the Galaxy.  This emission is more than 10,000 times stronger than the Cosmic Dawn signal.  Fortunately, the synchrotron spectrum is well-known and should be distinct from the expected Cosmic Dawn signal.  In principle, a good instrument will be able to distinguish between the two.  However, small instrumental imperfections can cause the synchrotron spectrum to look somewhat like the cosmological signal. Our recent upgrades to OVRO-LWA should help to overcome some of these instrumental effects.  

Cosmic-Rays

Cosmic rays are charged particles–the nuclei of atoms—travelling at nearly the speed of light and reaching Earth from other parts of our Galaxy or other galaxies. Some cosmic rays accelerate to energies millions of times higher than the highest energies that can be achieved in human-made particle accelerators on Earth.

When a cosmic ray collides with Earth’s atmosphere, it produces a cascading shower of particle collisions. The charged particles in the shower produce radio waves which can be observed from the ground. The OVRO-LWA will study high-energy cosmic rays by searching for roughly 10-nanosecond flashes of radio waves that sweep across the array with the signature pattern of a cosmic ray. Detecting and classifying cosmic rays from the radio data alone requires novel signal processing infrastructure to sift through 176 gigabytes per second of raw data to save short snapshots of air-shower events. The OVRO-LWA will study the composition of cosmic rays at the highest-energy limits of Galactic accelerators.

Dynamic Imaging Spectroscopy of the Sun

One of the major science topics of the OVRO-LWA is the physics of the Sun and its atmosphere. We have many reasons to study the Sun, ranging from the basic science of how the Sun produces the solar system’s biggest explosions, to the realization that other stars and planetary systems produce the same phenomena, which can only be studied in the minutest detail in our nearest star, to the very practical reason that the Sun affects our daily lives as well as the health of our technological infrastructure on the Earth and in space.

The OVRO-LWA operates in the frequency range 20-88 MHz, the so-called metric radio range because the corresponding wavelengths are about 3-15 meters. This band is very useful for probing a height range of 1.3 to 2 (solar radii, measured from the center of the Sun).  This is an important height range to study, because it is over this range that the solar wind is accelerated and the coronal structure at lower heights transitions to the “Parker spiral” magnetic structure that defines the remainder of the heliosphere.

Last Modified: 02/06/2025
Modified by: Gregg Hallinan