Oulu monitor, last day

6,083 counts/min

25/10/2026

rate corrected for pressure and efficiency

Oulu neutron monitor, daily corrected count rate (Sodankylä Geophysical Observatory) · Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · 10/25/26 Current

Modulation potential φ

908 MV

12/2025

last month published; high = protective Sun

Heliospheric modulation potential φ, monthly, from neutron monitors (University of Oulu) · Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · 10/25/26 Current

Sunspots → cosmic rays link

-0.85

r at 5 months; delay 2 months (even cycles), 15 months (odd)

Drop after a halo CME

-1.1 %

mean of 389 fast CMEs, minimum on day +4

Cosmic rays at ground level, Oulu, since 1964 (counts per minute, monthly means) Oulu neutron monitor, daily corrected count rate (Sodankylä Geophysical Observatory) · Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · 10/25/26 Current

Show the data as a table

Count rate of the Oulu neutron monitor (Finland), corrected for atmospheric pressure and detector efficiency. It falls by 15 to 25 % at every solar maximum: the active Sun and its wind shield the Earth from galactic cosmic rays. Cosmic-ray maxima are alternately peaked (1965, 1987, 2009) and flat-topped (1976, 1997, 2020): the mark of the 22-year magnetic cycle. The 2009 record follows the deepest solar minimum in a century.

Sunspot number since 1964 (monthly means) SILSO monthly mean total sunspot number V2.0 · CC BY-NC 4.0 · 10/23/26 Current · provisional

Show the data as a table

For comparison, over the same period: each sunspot maximum is answered, with a delay, by a dip in cosmic rays.

Heliospheric modulation potential φ since 1951 (MV) Heliospheric modulation potential φ, monthly, from neutron monitors (University of Oulu) · Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · 10/25/26 Current

Show the data as a table

Parameter of the force-field model that sums up the shielding of cosmic rays by the Sun, reconstructed from the whole world network of neutron monitors and calibrated on PAMELA space measurements (Usoskin et al., 2017). The maxima of 1957–1960 and 1989–1991 exceed 1,000 MV; the 1991 peak follows the very strong flares of June 1991.

Oulu, last 30 days (counts per minute, hourly values) Oulu neutron monitor, hourly corrected count rate (Sodankylä Geophysical Observatory) · Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · 10/25/26 Current

Show the data as a table

Hourly values: a Forbush decrease shows as a drop of a few percent within hours followed by a slow recovery; a sudden jump would signal a ground-level enhancement of solar protons (GLE), rare (73 since 1942).

Method and sources

Standard 6NM64 neutron monitor at Oulu (65.05° N, 25.47° E, geomagnetic cutoff rigidity about 0.8 GV), run by the Sodankylä Geophysical Observatory: daily count rate since April 1964 and hourly over the last 90 days, corrected for barometric pressure and efficiency. Monthly modulation potential φ since 1951, reconstructed by the University of Oulu. Data distributed for research, education and public non-commercial services; acknowledgement to cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory.

Reading these data

A neutron monitor counts the secondary neutrons produced in the atmosphere by cosmic rays of about 1 to 20 GV: it does not see the most energetic particles directly. Variations of a few percent in the daily rate can also come from snow on the detector or from atmospheric temperature, imperfectly corrected. The supposed link between cosmic rays and cloudiness (Svensmark) is not tested here: it needs homogeneous cloud data, which the Observatory does not have yet.

SOURCES OF THIS PAGE

Oulu neutron monitor, daily corrected count rate (Sodankylä Geophysical Observatory): Oulu neutron monitor data, cosmicrays.oulu.fi, Sodankylä Geophysical Observatory of the University of Oulu (6NM64 standard neutron monitor at 65.05° N, 25.47° E, geomagnetic cutoff rigidity ≈ 0.8 GV). · source page ↗
Licence : Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · retrieved on Oct 25, 2026 · SHA-256 fc2f77ecf31e…
Heliospheric modulation potential φ, monthly, from neutron monitors (University of Oulu): Usoskin, I. G., Gil, A., Kovaltsov, G. A., Mishev, A. L., & Mikhailov, V. V. (2017). Heliospheric modulation of cosmic rays during the neutron monitor era: calibration using PAMELA data for 2006–2010. J. Geophys. Res. Space Physics, 122, 3875–3887. · doi:10.1002/2016JA023819 · source page ↗
Licence : Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · retrieved on Oct 25, 2026 · SHA-256 566fb0417168…
SILSO monthly mean total sunspot number V2.0: SILSO World Data Center. The International Sunspot Number, V2.0. Royal Observatory of Belgium, Brussels. · source page ↗
Licence : CC BY-NC 4.0 · retrieved on Oct 23, 2026 · SHA-256 4749cc16c68e…
Oulu neutron monitor, hourly corrected count rate (Sodankylä Geophysical Observatory): Oulu neutron monitor data, cosmicrays.oulu.fi, Sodankylä Geophysical Observatory of the University of Oulu. · source page ↗
Licence : Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · retrieved on Oct 25, 2026 · SHA-256 2dd263a9b598…

Cosmic rays The Oulu neutron monitor since 1964, and the shield of the Sun