Owens Valley Solar Arrays

Owens Valley Solar Arrays (OVSA) is a university-led radio facility dedicated to solar astrophysics and space weather research. Located in the Owens Valley Radio Observatory (OVRO) near Big Pine, California, the operations of OVSA include the Expanded Owens Valley Solar Array (EOVSA) observing in the microwave regime (1-18 GHz), as well as the solar and space weather aspects of the newly commissioned Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA), which observes in the meter-decameter wavelength regime (13-87 MHz). Please refer to our home page for more general descriptions of the facility. This wiki serves as the site for OVSA documentation.

Operation of OVSA is supported by the National Science Foundation under Grant AGS-2436999. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Latest OVSA Science Highlights

OVSA Science Highlight No. 3: The First EOVSA "Cold" Solar Flare

This study takes advantage of EOVSA's microwave imaging spectroscopy capability and multi-wavelength observations to measure the coronal magnetic field and track the flare energy partitioning. The results show ample magnetic free energy to drive efficient electron acceleration, with the energy deposition of nonthermal electrons alone accounting for the observed thermal response, reinforcing cold flares as clean cases of particle-driven heating. [Contributed by Gregory Fleishman (New Jersey Institute of Technology); Edited by B. Chen. Posted on August 20, 2025.]

OVSA Science Highlight No. 2: Two Phases of Impulsive SEP Acceleration

M. Wang et al. analyze a solar energetic particle (SEP) event associated with an eruptive X-class flare and found two distinct impulsive SEP acceleration phases. They are suggested to link to different magnetic reconnection regimes during the eruption, which govern the timing and energy of particles released into interplanetary space. [Contributed by Meiqi Wang (New Jersey Institute of Technology); Edited by B. Chen. Posted on August 19, 2025.]

OVSA Science Highlight No. 1: Microwave Precursor of a Major Solar Eruption

A study by Y. Kou et al. presents the first spatially resolved microwave imaging spectroscopy of the precursor phase of a major solar eruption. The findings reveal that thermal electron emissions dominate during the slow-rise phase, supporting a scenario of moderate magnetic reconnection prior to the flare’s impulsive onset. [Contributed by Yuankun Kou (Nanjing University); Edited by B. Chen. Posted on August 2, 2025.]

We welcome contributions at all times. Please refer to the OVSA Science Highlights page for guidelines and a complete list of highlights.

OVSA Publications

Our collection of publications that utilize OVSA data is available at this NASA/ADS Library. If you have a paper that is missing from this library, please email Bin Chen (bin.chen [at] njit.edu).

EOVSA Flare List

• Query EOVSA Flare list
• List of EOVSA flares in separate years: 2025, 2024, 2023, 2022, 2021, 2020, 2019, 2017

Using OVSA Data

• EOVSA Data Products: An introduction to standard EOVSA spectrogram and spectral image products with example scripts for reading and plotting.
• OVSA Data Policy: Policy for using OVSA data products.
• Analysis Software: These are for in-depth use of EOVSA data (from calibrated visibilities) and tools for quantitative analysis.
  • SunCASA A wrapper around CASA (the Common Astronomy Software Applications package) for synthesis imaging and visualizing solar spectral imaging data. CASA is one of the leading software tool for "supporting the data post-processing needs of the next generation of radio astronomical telescopes such as ALMA and VLA", an international effort led by the National Radio Astronomy Observatory. The current version of CASA uses Python (2.7) interface. More information about CASA can be found on NRAO's CASA website . Note, CASA is available ONLY on UNIX-BASED PLATFORMS (and therefore, so is SunCASA).
  • GSFIT A IDL-widget(GUI)-based spectral fitting package called gsfit, which provides a user-friendly display of EOVSA image cubes and an interface to fast fitting codes (via platform-dependent shared-object libraries).
  • pyGSFIT A Python-widget(pyQT)-based spectral fitting package, which provides a user-friendly display of EOVSA image cubes, spatially resolved spectra, and an interface to scipy-based fitting codes.
  • Spectrogram Software
  • Mapping Software
• Data Analysis Guides (for those who start from raw data)
  • Tohban Guide to Self Calibration and Imaging for EOVSA Step-to-step guide for manually making images from raw visibility data.
  • EOVSA flare pipeline Description of the EOVSA flare pipeline and tutorial for running it to produce quicklook images.

• EOVSA Modeling Guide
  • GX Simulator

• Other helpful links
  • CASA Guides
  • SolarSoft IDL
  • Miriad Guides
  • Fast Gyrosynchrotron Codes (Alexey Kuznetsov's website)
  • Basic GitHub Tutorial

• Full Disk Simulations
• All-Day Synthesis Issues
• Analyzing Pre-2017 Data
• Fixing Pipeline Problems pre-2021-Feb-07

EOVSA Documentation

• General
  • Downconversion and Frequency Tuning
  • Dealing with Radio Frequency Interference
  • Switching between 200 MHz and 300 MHz Correlator
  • Observing in "Fast" Mode

• Computer-Network
  • Computing Systems
  • Network

• Control System
  • 27-m Antenna Commands
  • Schedule Commands
  • Control Commands
  • Attenuation and Level Control

• Hardware
  • Hardware Overview
  • 2.1-m Antennas
  • 27-m Antennas

• System Software
  • Calibration Database
  • Stateframe Database
  • Database Maintenance
  • Create CASA measurement sets

• Calibration
  • Calibration Overview
  • Pointing Calibration
  • Total Power Calibration
  • System Gain Calibration
  • Antenna Position (Baseline Calibration)
  • Reference Gain Calibration
  • Daily Gain Calibration
  • Delay Calibration
  • Bandpass Calibration
  • Polarization Calibration
  • Calibrator Survey
  • Practical Calibration Tutorial

• Starburst

EOVSA System Software

• LabVIEW software
• Python code Github repository
• Python3 Code Installation

Using OVRO-LWA data

• OVRO-LWA Data Products: An introduction to standard OVRO-LWA spectrogram and spectral image products with example scripts for reading and plotting.
• OVRO-LWA Data Policy: Policy for using OVRO-LWA data products.

EOVSA Observing Log

2016 November; December

2017 January; February; March; April; May; June; July; August; September; October; November; December

2018 January; February; March; April; May; June; July; August; September; October; November; December

2019 January; February; March; April; May; June; July; August; September; October; November; December

2020 January; February; March; April; May; June; July; August; September; October; November; December

2021 January; February; March; April; May; June; July; August; September; October; November; December

2022 SQL Outage

2023 January; February; March; April; May; June; July; August; September; October; November; December

2024 January; February; March; April; May; June; July; August; September; October; November; December

2025 January; February; March; April; May; June; July; August; September; October; November; December

OVSA Scientist on Duty

• Scientist on Duty (SoD): OVSA team members take turns and serve as a SoD to work with our onsite observatory staff on day-to-day observing. They are also responsible for monitoring solar activities and ensuring that the data we collect is of high quality.
• SoD observing logs (directory to all logs):
  • 2024: May (and before that), June, July, August, September, October, November, December
  • 2025: January,February, March, April, May, June, July, August
• SoD instructions:
  • Daily routines: see SoD Routines for detailed instructions.
  • Instructions for making quick-look flare spectrograms and movies

OVRO-LWA Solar-Dedicated Spectroscopic Imager

The OVRO-LWA (Owens Valley Radio Observatory Long Wavelength Array) has recently been upgraded to include a solar-dedicated beam and two solar imaging modes (slow visibilities of 352 antennas with a 10-s cadence, and fast visibilities of 48 antennas with a 0.1-s cadence). The large collecting area and excellent calibration provide unprecedented high-sensitivity imaging of the quiet Sun and bursts. The array is currently in commissioning and observations are not yet continuous, but they are becoming more so. See the daily realtime data at http://ovsa.njit.edu/status.php for real-time display of the spectrogram and a selection of images, both updated on a 1-min cadence.

Solar-Dedicated Modes

• Beamformer: The OVRO-LWA beamformer uses the 256 antennas in the core region to form a synthesized beam of more than 1 degree in size that tracks the Sun from sunrise to sunset. This permits a continuous record of the full-Stokes total flux (without spatial resolution) of the Sun (a dynamic spectrum) with 24 kHz frequency resolution (3072 frequencies from 13.4-86.9 MHz) and as low as 1 ms time resolution.

• Standard Interferometric Imaging (also known as "Slow Visibilities"): In this mode, the entire 352-element array is interferometrically correlated to provide visibilities for imaging at all 3072 frequencies at 10-s time resolution. This is ideal for imaging quiet Sun and slowly-varying emission such as coronal mass ejections and active region variability.

• Bursty Interferometric Imaging (also known as "Fast Visibilities"): In this mode, a subset of 48 antennas (chosen to include mainly outer antennas to maintain good spatial resolution) is interferometrically correlated to provide visibilities for imaging at 768 frequencies (96 kHz frequency resolution) at 0.1-s time resolution. This is ideal for imaging rapidly varying emission such as type II and type III bursts as well as many other solar spectral fine structures.

Data Access

• OVRO-LWA solar data release v1.0 is available! Please refer to the OVRO-LWA Data Products page for more information.

OVRO-LWA Operation Notes

OVRO-LWA Operation Notes

Tohbans

Trouble Shooting Guide

Tohban Records

Owen's Notes

Caius' Notes

Tohban EOVSA Imaging Tutorial A-Z

Tohban OVRO-LWA Imaging Tutorial

Tohban Guide to Self Calibration and Imaging for EOVSA

Guide to Upgrade SolarSoft(SSW)

Star Pointing Notes

VLA Flare List and Publications

See this link for a list of flare observations made by the Karl G. Jansky Very Large Array (VLA). Below is a partial list of publications that utilize VLA solar data (see also this NASA/ADS Library).

• Luo et al. (2022), ApJ, 940, 137 Multiple Regions of Nonthermal Quasiperiodic Pulsations during the Impulsive Phase of a Solar Flare
• Battaglia et al. (2021), ApJ, 922, 134 Multiple Electron Acceleration Instances during a Series of Solar Microflares Observed Simultaneously at X-Rays and Microwaves
• Luo et al. (2021), ApJ, 911, 4 Radio Spectral Imaging of an M8.4 Eruptive Solar Flare: Possible Evidence of a Termination Shock
• Zhang et al. (2021), ApJ, 910, 40 Multiwavelength Observations of the Formation and Eruption of a Complex Filament
• Sharma et al. (2020), ApJ, 904, 94 Radio and X-Ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare
• Chen et al. (2019), ApJ, 884, 63 Radio Spectroscopic Imaging of a Solar Flare Termination Shock: Split-band Feature as Evidence for Shock Compression
• Yu & Chen (2019), ApJ, 872, 71 Possible Detection of Subsecond-period Propagating Magnetohydrodynamics Waves in Post-reconnection Magnetic Loops during a Two-ribbon Solar Flare
• Chen et al. (2018), ApJ, 866, 62 Magnetic Reconnection Null Points as the Origin of Semirelativistic Electron Beams in a Solar Jet

• Wang et al. (2016), ApJ, 848, 77 Dynamic Spectral Imaging of Decimetric Fiber Bursts in an Eruptive Solar Flare
• Chen et al. (2015), Science, 350, 1238 Particle acceleration by a solar flare termination shock
• Chen et al. (2014), ApJ, 794, 149 Direct Evidence of an Eruptive, Filament-hosting Magnetic Flux Rope Leading to a Fast Solar Coronal Mass Ejection
• Chen et al. (2013), ApJL, 763, 21 Tracing Electron Beams in the Sun's Corona with Radio Dynamic Imaging Spectroscopy

Radio Data from Around The Heliosphere

• Radio Data

Radio Astronomy Lecture Notes

Here is a link to the Radio Astronomy Lecture Notes adapted from the Phys728: Radio Astronomy graduate-level course Prof. Dale Gary taught at NJIT until Spring 2019.