Identification

Title

Secular changes in the thermosphere and ionosphere between two quiet Sun periods

Abstract

The solar minimum period between solar cycles 23 and 24 was the longest since the beginning of space-based measurements, and many manifestations of solar activity were unusually low. Thermospheric neutral density was about 30% lower than during the previous solar minimum, but changes in the ionosphere between the two solar minima are more controversial. Solar radiation, geomagnetic activity, and anthropogenic increases in greenhouse gases can all play a role in these changes. In this paper, we address the latter of these potential contributions the degree to which secular change driven by greenhouse gases, primarily CO₂, could be responsible for the observed changes. New 3-D model simulations find a global mean density decrease at 400 km of 5.8% between the two recent solar minima, which is larger than earlier 1-D model results and in better agreement with observations. From these model simulations and from other observational work, we estimate that the contribution of secular change to global mean neutral density decrease between the two recent solar minima is less than ~6%. The contribution of secular change to the global average decrease of F region ionosphere peak density (NmF2) and altitude (hmF2), near midday, is estimated to be 1.5% and 1.5 km, respectively. However, secular changes in the ionosphere exhibit large variations with local time, geographic location, and season. The midday change of NmF2 seen in the model simulations ranged between +6% and -9% and the change of hmF2 ranged between +11 km and -11 km, depending on geographic location.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7k35vmr

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2014-03-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact