The solo_L2_rpw-tds-surv-rswf-e data provide TDS regular waveform snapshots with up to three electric components, measured in both SURVEY NORMAL and BURST modes with a sampling frequency of 262 kHz or 524 kHz. The regular snapshots are collected periodically. The time cadence is configurable but typically one snapshot every 1-5 minutes.
The L2 files contain electric field waveform data calibrated to physical units both in antenna coordinates and in spacecraft reference frame (SRF) coordinate system (because the three RPW antennas are mounted in a single plane, only two components of electric field are provided. Furthermore, the waveforms are also provided with a simpler calibration, converted to voltage by a constant calibration factor. This is useful if the user prefers to apply a different antenna calibration matrix.

DOI: https://doi.org/10.57780/esa-3xcjd4w

Data organization

Each CDF record in the file contains a waveform snapshot (time series) for up to three channels of the electric field, as indicated in CHANNEL_ON. The same waveform data are represented in multiple forms in the file:

• The calibrated electric field data (V/m) in sensor coordinates is stored in WAVEFORM_DATA variable. This data is calibrated to V/m using a frequency dependent calibration function, inverting the receiver and preamplifier transfer functions. Each component of the waveform corresponds to measurement from a single antenna (either monopole or differential, depending on input configuration). The individual components are thus not orthogonal.
• If applicable, the same calibrated E-filed also transformed into orthogonal Y-Z SRF components, stored in E_FIELD_Y_SRF and E_FIELD_Z_SRF variables. Since all RPW antennas are mounted in a single plane, only two orthogonal components are available.
• Additionally, calibrated voltage data is stored in WAVEFORM_DATA_VOLTAGE. This data corresponds to the same receiver channels as WAVEFORM_DATA, but it is only calibrated as voltage (either voltage between the antenna and the spacecraft in the case of monopoles or voltage difference between two antennas in the case of dipoles). This voltage calibration is done in a simpler way, using a constant, frequency independent factor for each antenna, corresponding to instrument gain at approximately 50 kHz.

The Epoch time of each record represents the acquisition time of the first data sample in the snapshot. To reconstruct the time vector for a given snapshot, the number of nanoseconds stored in EPOCH_OFFSET (INT4) must be added to Epoch (CDF_TIME_TT2000).

The snapshot length (in samples per channel) is stored for each snapshot in SAMPS_PER_CH variable (same length applies to WAVEFORM_DATA, E_FIELD_Y_SRF, E_FIELD_Z_SRF, and WAVEFORM_DATA_VOLTAGE). The dimensions of these variables are not necessarily constant across files and the length of the array can be larger than SAMPS_PER_CH in which case only the first SAMPS_PER_CH samples are valid, the rest should be FILLVAL. The global attribute WAVEFORM_DATA_LENGTH stores the maximum number of samples per snapshot for the given file.

The WAVEFORM_DATA and WAVEFORM_DATA_VOLTAGE variables contain in general multiple signal components from individual antennas, each component represented by one row of the matrix. The valid channels are indicated by a non-zero value in the corresponding element of CHANNEL_ON variable and the dipole/monopole antenna configuration for each channel can be found in CHANNEL_REF variable in numeric form or in CHANNEL_LABEL in text form. In a vast majority of cases, only the three standard configurations listed in Table 1 are used but sometimes only the first two components are stored.

Missing or invalid data samples are represented using FILLVAL.

Caveats and known issues

Table below gives the list of main known issues and the actions taken to mitigate them.
Please read the CAVEATS global attribute entries in the CDF files to be aware of the possible issues and limitations concerning data.

Release notes

See MODS global attribute in the CDF files for an history of the data modifications.

Authors

David Pisa, and Jan Soucek.

References

• The Solar Orbiter Radio and Plasma Waves (RPW) instrument, Maksimovic et al., A&A, 2020 (https://doi.org/10.1051/0004-6361/201936214)
• Metadata Definition for Solar Orbiter Science Data, Helen R. Middleton
• RPW Data Product Description Document (DPDD)
• NASA CDF Web portal

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