Event Lists

The Heliophysics Event Catalogue (HEC), developed within the HELIO project, contains the most comprehensive set of event lists for phenomena that have occurred throughout the heliopshere.

Types of Event

Different types of event list are included in the HEC from a variety of locations in the heliosphere. For some phenomena we have included lists describing the same events created by different groups and, in some cases, observed from different vantage points. The Master Catalogue shows how the different lists have been tagged within the HEC in terms of event type and observing domain.

Flares observed in several different wavelengths – soft and hard X-rays, H-alpha, EUV – from observatories in various locations in the heliosphere. Some of the flares included are from locations on the far side of the Sun.

Coronal Waves – planning to include a more complete lists.

Coronal Mass Ejections (CMEs) observed in different parts of the heliosphere, using both remote-sensed and in-situ measurements. The remote-sensed CME lists include one derived by hand from the SOHO coronagraph data and others derived using automated techniques (CACTUS and SEEDS) for SOHO and the STEREO spacecraft. There are in-situ lists derived from observations of the phenomena from the SOHO, STEREO spacecraft and the Ulysses mission. Where possible we have attempted to include lists that complement each other – for example remote-sensed observations from SOHO and in-situ from STEREO and Ulysses, and visa versa. A list derived from the J-plots created using STEREO-HI observations is also included.

Solar Energetic Particle (SEP) events observed in different parts of the heliosphere. Not all flares produce protons; some from shock front of CMEs. When observed from the Earth, Ground Level Enhancements (GLEs) and Forbush Decreases are relevant.

Various solar wind phenomena including: Shocks, Stream Interaction Regions (SIRs or CIRs), ICMEs

Selection Criteria

There are no definitive event lists; all lists embody someone's concept of what represents an event, based on their own criteria. In addition, since the data sets from which lists are derived sometimes have gaps, the lists are not necessarily complete. An individual list should therefore be treated with caution and should ideally be viewed in the context of other information; often using event lists of the same type collectively provides the best understanding of what has happened.

Within the HELIO project we have therefore tried to seek out as many event lists as we can find from as many different sources as possible; we leave it up to the user to decide how to use the lists, which are most valid, etc. for their particular science use case.

Event lists related to proton events are amongst the most contentious. For example, there are arguably deficiencies in the proton event list produced by NOAA. In this list an event is defined as the time that the 10 MeV flux is above a certain threshold but, because low energy particles can persist for many days, events that occur within the time envelope that could be more intense at higher energies can be masked and are thus not identified. By seeking out as many different proton event lists as possible – some of which are based on different criteria – the user has the chance to see that other events have occurred without having to view the time-series data.

Note that it is important to understand whether the observations can support the criteria that are being used to define an event. For example, EUV waves have always existed but but could not be properly detected using SOHO/EIT data because the image cadence is too low; any event list based on the EIT is therefore incomplete. SDO/AIA has a cadence that is high enough for such constraints not to be an issue.

Gaps in Coverage

Events lists can sometimes be incomplete and this can lead to confusion. Flares observed at one wavelength may on occasions be absent from lists at another wavelengths as a consequence of gaps in the data rather than because they did not occur.

The list of solar flares produced from the X-ray Sensor (XRS) on GOES is almost complete because the (multiple) spacecraft are in geostationary orbit giving nearly 100% coverage. However, many other observatories only observe the Sun for a part of the day and are subject to different types of interruptions.

Observations that are made from a ground-based observatory – either on the Earth or another planet – will possibly miss events that occur in a different frame of reference. Except for a few months each year at the Poles, the Sun cannot be seen from the ground for the whole day, weather can also reduce the time when observations can be made.

Similarly, spacecraft in low Earth orbit (LEO) have times in their orbit when they Sun cannot be seen; high inclination orbits are chosen for some missions because the such sun-synchronous orbits mean that the Sun can be seen for months at a time. Passage through radiation belts can further reduce the observing time for some types of detectors.

There are periods when an instrument is not producing data for other reasons. For example, some detectors need to conditioned at regular intervals to ensure optimal performance; in this category are RHESSI annealing and SOHO/EIT bake-out.

There have also been periods where observations could not be made for more extreme reasons, because of spacecraft issues. Such spacecraft outages include: the time that the SOHO mission was lost for several months; when the STEREO-A spacecraft was on the other side of the Sun.

Audit of the lists in the HEC

This Audit provides the latest summary of the lists that are available in the HEC and the date ranges that they cover. The status of the lists are classified as shown in the table below. Included in the Audit are links to the description of the contents of each list; we have tried to fully annotate the parameters and include caveats that help the user understand how they should be used.

Active	The catalogue is being updated automatically, either daily or on a less regular basis.
Static	Updating of the catalogue is sporadic because of issues either on the provider side or on the HEC service side.
Inactive	The catalogue has not been updated for an extended period. Possible reasons: i) The catalogue has changed format or location and HELIO has not updated ingestion; ii) It could be updated using available data but it is not clear that the provider intends to do this; iii) The data flow of the relevant instrument has been interrupted and it is not clear if or when it will resume.
Closed	The catalogue updating has definitively stopped and will not be resumed. This category includes lists derived from Journal articles.

Note that old event lists have been removed from the HEC when a superior version of a list has been identified, .

 
Last updated: 23rd August 2016