Expansion of the Heliosphere
This data release incorporates IBEX data products from the publication McComas et al. (2018) “Heliosphere Responds to a Large Solar Wind Intensification: Decisive Observations from IBEX”. Compton-Getting (CG) corrections have been applied to the data to account for the speed of the spacecraft relative to the direction of arrival of the ENAs. It includes the subset of additional CG maps used in the paper which were not included in the 7 year data release. See the 7 year data release website for additional file descriptions.
Abstract: Our heliosphere — the bubble in the local interstellar medium produced by the Sun’s outflowing solar wind — has finally responded to a large increase in solar wind output and pressure in the second half of 2014. NASA’s Interstellar Boundary Explorer (IBEX) mission remotely monitors the outer heliosphere by observing energetic neutral atoms (ENAs) returning from the heliosheath, the region between the termination shock and heliopause. IBEX observed a significant enhancement in higher energy ENAs starting in late 2016. While IBEX observations over the previous decade reflected a general reduction of ENA intensities, indicative of a deflating heliosphere, new observations show that the large (∼50%), persistent increase in the solar wind dynamic pressure has modified the heliosheath, producing enhanced ENA emissions. The combination of these new observations with simulation results indicate that this pressure is re-expanding our heliosphere, with the termination shock and heliopause already driven outward in the locations closest to the Sun. The timing between the IBEX observations, a large transient pressure enhancement seen by Voyager 2, and the simulations indicates that the pressure increase propagated through the heliosheath, reflected off the heliopause, and the enhanced density of the solar wind filled the heliosheath behind it before generating significantly enhanced ENA emissions. The coming years should see significant changes in anomalous cosmic rays, galactic cosmic radiation, and the filtration of interstellar neutral atoms into the inner heliosphere.
Plots and Data Directories
Yearly Maps, Ram Direction
These maps include data recorded from times when the aperture was pointed towards the hemisphere of the spacecraft’s motion. The maps do not include survival probability corrections. Compton-Getting maps adjust values after correcting for the speed of the spacecraft in relation to the direction of arrival of the ENAs.
The data directories:
Yearly Maps, AntiRam Direction
These maps include data recorded at times when the aperture was pointed away from the hemisphere of the spacecraft’s motion. The maps do not include survival probability corrections. Compton-Getting maps adjust values after correcting for the speed of the spacecraft in relation to the direction of arrival of the ENAs.
The data directories:
The first number in the first line of each data file gives the number of lines taken up by the header followed by the number of rows times the number of columns in the data (i.e. 30X60 indicates 30 rows of declination by 60 columns of right ascension values). Row 1 corresponds to the South Ecliptic Pole, while row 30 corresponds to the North Ecliptic Pole. The columns start at ecliptic longitude 0 and step through to ecliptic longitude 360; the values of the first and last columns in each map are identical. The layout of the columns corresponds to Solar Ecliptic East Longitude, right to left as seen outward by IBEX. The keyword “h_title” gives the description of the data and the units used.
Figure 2 of McComas et al. 2018: Comparison of ENA fluxes from late 2015 to late 2016 from CG corrected anti-ram data. We show data for the highest two energies, where a visible increase in ENA intensity is detected in late 2016.
Figure 4 of McComas et al. 2018: Comparison of ENA fluxes from early 2016 to early 2017 from CG corrected ram data. The IBEX Ribbon is visible in the lowest energies, 0.7 and 1.1 keV. At higher energies, the ENAs are progressively enhanced with increasing energy from the 1.7 to 2.7 to 4.3 keV energy bands, consistent with the greater generation and faster return of higher energy ENAs calculated by the numerical model.