The Mexican Array Radio Telescope (MEXART) is a transit instrument dedicated to interplanetary scintillation (IPS) observations from compact radio sources . The instrument has 16 fixed latitudinal beams pointing towards different declinations and uses the Earth's rotation to scan the whole sky. The angular width of the beams along the east–west direction is about 1 ∘, so a discrete radio source has a transit of about 4 min in the data series and the Sun around 8 min. The basic elements of the radio telescope are full wavelength dipoles (λ=2.14 m). The radiotelescope performs observations at a frequency of 139.65 MHz with a bandwidth of 2 MHz. More details of the instrument can be found in .

The telescope allows us to remotely infer some characteristics of solar wind streams crossing along the line of sight of the extragalactic radio sources detected by the instrument. This includes the tracking of large-scale interplanetary perturbations. The solar wind speeds and interplanetary density fluctuations along the lines of sights are computed with the use of the methods developed by SCiESMEX. When the line of sight of a radio source passes across the solar wind electronic density inhomogeneities, the radio signals are scattered, and a diffraction pattern is produced.

To infer some solar wind characteristics (velocity and density fluctuations) from the IPS data, we apply a power spectra analysis to record the transit of the radio source. We employ a theoretical model to obtain a power spectrum of the IPS fluctuations. This IPS theoretical spectrum incorporates different physical parameters, including solar wind speed. We fit the theoretical model to the observed power spectra, obtaining the solar wind speed that best matches the observation. The solar wind speed location is assumed at the nearest point of the Sun to the line of sight. The solar wind density fluctuations are estimated from the area under the curve of the observed IPS spectrum; this area is equivalent to the scintillation index m. Further details about the MEXART methodology can be found in . The results of IPS observations are published weekly in the SW reports

Reports can be found on the official web page of SCiESMEX (http://www.sciesmex.unam.mx/blog/category/reporte-semanal-de-clima-espacial/, last access: 5 October 2018).

Solar radio bursts are spontaneous emissions of electromagnetic waves at low frequencies in the outer solar atmosphere produced by shock waves close to the corona or in the interplanetary medium . The signal received on Earth is interpreted as an increase of the radio noise that is analyzed continuously by many solar radio spectrum observatories . The global e-CALLISTO network is among these observatories .

In 2015, a CALLISTO (Compact Astronomical Low-frequency, Low-cost Instrument for Spectroscopy in Transportable Observatories) station was installed in the facilities of the MEXART radio telescope (CALLISTO-MEXART station). This station forms part of the e-CALLISTO network. Up to now, about 100 solar radio events have been detected, and their radio noise spectrum at the site has been categorized . The observations are only performed during daylight hours, with 200 different channels ranging from 45.7 to 344.7 MHz captured every 15 min with a resolution of 250 ms.

The product related to CALLISTO is the dynamic radio spectrograph; see the example in Sect. . Its results are published every 15 min on the web pages of RICE and the e-CALLISTO international network.

The Mexico City Cosmic Ray Observatory is equipped with two instruments: a muon telescope and a neutron monitor (NM). The muon telescope detects the hard component (negative and positive muons) produced by the decay of charged pions, which are produced by interactions of the primary cosmic rays with the atmospheric nucleus. It is composed of eight plates of a plastic scintillator; four plates are located above the NM and four under it. The muons crossing through the scintillators lose energy by ionization and produce fluorescent radiation that travels to a photomultiplier . The Mexico City NM type is a 6-NM64. The monitor has worked continuously since 1990. Following , the mean energy response for the Mexico City NM is estimated as 24.5 GV; thus the instrument detects the low energy component of the galactic cosmic rays.

The cosmic ray observatory can detect flux variations caused by solar activity, for example, when a coronal mass ejection (CME) strikes the Earth and produces a sudden reduction in galactic cosmic ray flux intensity. This kind of event is known as a Forbush decrease (FD) . The cosmic ray intensity may have a drastic decrement up to 20  % in a few hours and the recovery is slow, typically around 7 to 10 days. It is one of the extreme manifestations of a transient modulation of galactic cosmic rays (GCRs). FDs are generally correlated with stream interaction regions, interplanetary shocks, and/or CMEs originated from the Sun . The FDs are observed by ground-based particle detectors, such as an NM. The phenomenon is produced by the irregularities in the interplanetary magnetic field associated with these large-scale solar wind disturbances that deflect the cosmic ray flux, causing a reduction in the number of cosmic rays detected at ground level . The product developed by SCiESMEX computes the cosmic ray flux in real time. The results are included in the SW weekly report.

The Teoloyucan Geomagnetic Observatory (TEO) is located near Mexico City (at latitude 19.746∘ N and longitude 99.19∘ W) and is managed by the Magnetic Service at the Geophysics Institute, UNAM. It performs the measurements of the geomagnetic field components (D, H, and Z) with a local magnetometer. The sampling rate is 5 s integrated by 1 min, and the baseline is continuously calibrated by the Magnetic Service's work team.

Since 2017, SCiESMEX, in collaboration with the Magnetic Service, has estimated the local geomagnetic field changes with the Kmex index. Kmex is the analog of the Kp index but on a regional scale (3 h measurements of the maximum absolute variations of the horizontal component (H); ). In agreement with the Kp index, the values of Kmex run from 0 to 9, with 0 representing a quiet state and 9 representing a saturated value for the most disturbed states. Each Kmex level relates almost logarithmically to H deviations from its quiet baseline .

The quiet baseline is calculated by statistically removing the systematic diurnal and monthly variations of H. The algorithm of Kmex calculation obtains values consistent with those reported with its planetary counterpart (Kp). At present, for the Kmex calculation, we use data from the Teoloyucan magnetic observatory only; consequently, currently Kmex values are only regionally representative of central Mexico. In the future, we will increase our coverage with several magnetometers in the Mexican territory. This will substantially increase the Kmex coverage as well as our space weather monitoring capabilities. It is important to remark that Kmex is under development, and its data sets are not definitive. Further details on Kmex calculations can be found in and general K-index calculations in and .

There are different GPS receiver networks operating in Mexico . Data from these networks are used to monitor SW effects on the ionosphere over the country. Vertical total electron content (TEC) values are obtained from RINEX files of local GPS stations with the use of two methods. In the first, calculations are performed using the US-TEC software , which is an operational product at the Space Weather Prediction Center (SWPC), developed through a collaboration between the National Geodetic Survey, SWPC by the National Oceanic and Atmospheric Administration (NOAA), and the Cooperative Institute for Research in Environmental Sciences of the University of Boulder, Colorado, United States. US-TEC allows near-real-time monitoring of TEC to be performed over the region through the maps that can be constructed in quasi-real time. For the detailed method description and its benefits, readers are referred to and . In addition, the TayAbsTEC method is also used for TEC calculations. Its advantage is that the receiver coordinates (specifics of the region) are taken into account. Detailed description and benefits can be found in and . Both methods proved to provide satisfactory results for TEC estimation in the region; see the references cited above.

The near-real-time TEC maps over Mexico are one of the products developed by SCiESMEX. The results of TEC estimation by different methods and the ionospheric W index as a measure of ionospheric disturbance are published in the SW weekly reports.

In 2015, the National Council of Science and Technology created a network of repositories for science and technology in Mexico. SCiESMEX manages the repository of the SW data. RICE provides the capabilities for massive and high-speed storage and processing of data from the networks of local and international SW instruments. The data in RICE can be processed in quasi-real time. The results are published on the official SCiESMEX web page both in weekly SW reports and as quasi-real-time SW values. This allows us to perform the continuous quasi-real-time monitoring of SW conditions and to analyze previous events.

On 19 June 2015 at 05:00 UTC, a filament eruption was detected in the solar southeast quadrant of the solar disk. On 21 June 2015, between 01:00 and 03:00 UTC, two solar flares erupted from the active region 2371 (M2 and M2.6), and a halo CME, associated with these flares, was also detected. On the same day, at 09:44 and 18:20 UTC, two other flares were released from the solar atmosphere, with M3 and M1 categories, respectively .

On 22 June 2015, two CME arrivals were detected by the ACE spacecraft at 04:51 UTC (associated with the first filament eruption) and 17:59 UTC (associated with the double-peaked M2 flare from the active region 2371 on 21 June). Shortly afterward, in the same active region, an M6 X-ray solar flare with a full halo CME was detected at 17:59 UTC. This last CME arrived at Earth 2 days later on 24 June at 12:58 UTC .

The second event that we address in this study is related to the solar radio burst. It was detected by the CALLISTO-MEXART station and the MEXART radio telescope at 19:22 UTC on 2 September 2015. This solar radio burst was associated with a weak M1.1 solar flare that started at 19:20 UTC, peaked at 19:24, and ended at 19:27 UTC. The closest CME related to this event was recorded by LASCO at 20:00:04 UTC. According to SWPC/NOAA this particular CME did not hit the Earth .

The solar radio event registered by CALLISTO-MEXART (Fig. ) shows the characteristic dynamic solar spectrum of a radio burst type III. The type II and type III spectrums differ in their dynamics. While type III shows an emission in consecutive short periods (minutes) of time and covers a wide wavelength bands, the type II radio burst is derived from high to low frequencies for a long period of time (days) . Related to this event, SWPC releases an ALTTP2 code where a type II burst at 19:30 UTC was reported (serial number: 1025). The type III solar radio burst was confirmed by two independent CALLISTO stations: Roswell, New Mexico, and Alaska (Fig. ). Figure  shows the light curve of the event constructed on the basis of CALLISTO data. The maximum peak of the event was characterized by a signal-to-noise ratio (SNR) of 32.

Both instruments, the MEXART radio telescope and the CALLISTO-MEXART, have a common band: approximately 140 MHz. Consequently, both instruments can detect the same events.

We rescaled (y axis) the fluxes obtained by two instruments to compare them. The results are given in Fig. , where we show the event observed at the same band by both instruments. We see that the solar radio burst was detected by both instruments. This is the first record of a solar radio burst type III by the MEXART radio telescope confirmed by the CALLISTO station simultaneous observation. The flux registered by both instruments opens the possibility of using MEXART as a solar radio monitor (not only for IPS observations) with high time resolution and a better sensitivity. The SNR only for the 140 MHz channel of CALLISTO is 18, and for the MEXART, it is 224 for the closest band.

The records show several disturbances in radio communications between 50 and 75 MHz and radio noise between 110 and 170 MHz for around 2 min at the site of observation. This is the first spectrum that shows a radio blackout over Mexico related to SW. This radio blackout could probably affect the frequencies lower than 50 MHz. The local time of the radio burst was about 11:20, close to noon locally. The ionosonde measurements could provide us with information if the HF band (3–30 MHz) was affected by the event. As mentioned above, SCiESMEX currently has no ionosonde measurements in Mexico. The installation of the ionosondes for oblique ionospheric sounding is planned for our future work.